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Q113641: README.TXT: Microsoft MS-DOS 6.21 Upgrade (Part 1 of 3)

Article: Q113641
Product(s): Microsoft Disk Operating System
Version(s): 6.21
Operating System(s): 
Keyword(s): 
Last Modified: 06-FEB-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft MS-DOS operating system version 6.21 
-------------------------------------------------------------------------------

SUMMARY
=======

The following information was taken from the MS-DOS 6.21 Upgrade README.TXT
file.

MORE INFORMATION
================

README.TXT

MS-DOS 6.21 does not include data compression. It differs from MS-DOS 6.2 as
follows:

- DoubleSpace is not included. For more information, see Section 7 of this
  file.

- ScanDisk will not run on DoubleSpace drives unless DoubleSpace is installed
  (that is, DBLSPACE.BIN is loaded in memory).

- The Backup programs do not compress data while backing up, and cannot restore
  compressed backups made by previous versions of Microsoft Backup. (By
  default, Setup does not replace your current version of Backup, if any). For
  more information, see section 5.5 of this file.

NOTES ON MS-DOS 6.21
--------------------

This file provides important information not included in the MICROSOFT MS-DOS
USER'S GUIDE or in MS-DOS Help.

This file is divided into the following major sections:

1. Setup

2. MemMaker, EMM386, and Memory Management

3. Windows

4. Hardware Compatibility with MS-DOS 6.21

5. Microsoft Programs

6. Third-Party Programs

7. DoubleSpace

If the subject you need information about doesn't appear in this file, you might
find it in one of the following text files included with MS-DOS:

- OS2.TXT, which describes how to remove and save data on your computer when
  you replace OS/2 with MS-DOS 6.21.

- NETWORKS.TXT, which describes how to update your network software for use
  with MS-DOS 6.21.

For information about new features, type "HELP WHATSNEW" (without the quotation
marks) at the command prompt.

This file contains the following topics:

1. Setup

  1.1  SpeedStor
  1.2  Incompatible Hard Disk or Device Driver
  1.3  AT&T 6300 Computer
  1.4  Toshiba with a Hard RAM Disk
  1.5  Tandy with ROM DOS
  1.6  Setup displays the "Your computer uses a disk-compression
       program that is incompatible with Setup" message.
  1.7  You deleted files from the directory that Setup needs
       to install the optional Windows programs.
  1.8  Running Setup if Your Computer Uses Windows NT
  1.9  Setup detects that your computer has a non-MS-DOS
       partition or non-MS-DOS files, and your computer uses Windows NT.
  1.10 Setup displays the "Your computer uses password protection"
       screen.
  1.11 Setup displays the "Your computer is using an incompatible
       delete-protection program" screen.
  1.12 Setup detects that your computer uses DR DOS.
  1.13 Installing MS-DOS on a Drive Other Than C
  1.14 Bypassing the Uninstall Disk and Using Default Setup Options
  1.15 Installing MS-DOS on a System with a CorelSCSI UNI_ASP.SYS Driver
  1.16 Installing MS-DOS if you have DrivePro or EZ-Drive
  1.17 Setup displays the "There is not enough disk space" screen
       and you are running PC-DOS version 6.1
  1.18 Setup cannot update a file
  1.19 Upgrading from PC-DOS 6.1

2. MemMaker, EMM386, and Memory Management

  2.1  Intel Expanded-Memory Driver (EMM.SYS)
  2.2  Running MemMaker on a Computer with PC-NFS
  2.3  You have a Super VGA display and want to conserve memory.
  2.4  Using MemMaker with IBM LAN
  2.5  MemMaker and Adaptec SCSI devices
  2.6  Running MemMaker on a computer with PC Tools RAMBoost
  2.7  EMM386 detects an error in an application
  2.8  MemMaker no longer aggressively scans upper memory by default

3. Windows

  3.1  Your computer uses a Windows 3.0 permanent swap file.
  3.2  Using compressed floppy disks with Windows File Manager

4. Hardware Compatibility with MS-DOS 6.21

  4.1  Compaq EXTDISK.SYS Driver
  4.2  Hardcard
  4.3  Toshiba

5. Microsoft Programs

  5.1  Microsoft Anti-Virus
  5.2  Running Microsoft Backup for MS-DOS under Windows
  5.3  Backup for Windows stops running at the end of the
       compatibility test
  5.4  Running Microsoft Backup with TI4000 and Gateway NOMAD computers
  5.5  MS-DOS 6.21 Backup Cannot Restore 6 or 6.2 Backups
  5.6  Microsoft Defragmenter

6. Third-party Programs

  6.1  4DOS and NDOS
  6.2  Above Board 286 and Above Board Plus Installation
       Programs
  6.3  CodeView
  6.4  Colorado Tape Backup
  6.5  Fastback Plus
  6.6  Norton Desktop for Windows 2.0
  6.7  Norton Utilities
  6.8  PC Tools
  6.9  QEMM's Stealth DoubleSpace Feature
  6.10 Johnson Computer Systems PC-Vault and PC-Vault Plus
  6.11 AddStor DoubleTools

7. DoubleSpace

  7.1  Converting Your XtraDrive Disk-Compression Software
       to DoubleSpace
  7.2  Converting Stacker 3.1 Software to DoubleSpace
  7.3  Converting Other Disk-Compression Software to DoubleSpace
  7.4  DoubleSpace Setup indicates that your computer is running an
       incompatible disk-caching program.
  7.5  Your compressed drive runs out of disk space.
  7.6  Your uncompressed (host) drive runs out of disk space.
  7.7  DoubleSpace did not compress all of your files because
       the drive ran out of disk space.
  7.8  Windows displays the message "The permanent swap file is corrupt."
  7.9  EXTDISK.SYS displays a warning about drive letters.
  7.10 You need a special device driver to use your startup drive.
  7.11 Defragmenting uncompressed drives after changing file attributes
  7.12 Files DoubleSpace cannot compress
  7.13 Microsoft Defragmenter runs out of memory while you are
       compressing a drive.
  7.14 DoubleSpace and PC-Vault
  7.15 Maximum size of a compressed drive
  7.16 DoubleSpace could not mount a drive due to problems with the drive
  7.17 DoubleSpace finishes installation, but you cannot access your
       Hardcard.
  7.18 You receive a DoubleGuard Alarm message
  7.19 A compressed drive is currently too fragmented to mount
  7.20 DoubleSpace displays the message "Your computer is running with an
       incompatible version of DBLSPACE.BIN"
  7.21 Using the DBLSPACE command after bypassing DBLSPACE.BIN
  7.22 Removing the write-protection from a compressed floppy disk
  7.23 Automounting and Norton Disk Cache
  7.24 Undelete utilities and DoubleSpace
  7.25 Creating an Emergency Startup Disk for DoubleSpace Systems
  7.26 If ScanDisk Cannot Check or Repair a DoubleSpace Volume File

1. SETUP
--------

1.1 SpeedStor:

If Setup referred you to this section and your computer has an OS/2 partition
created by using the FDISKPM utility in OS/2 2.1, run MS-DOS Setup by typing
"SETUP /U" (without the quotation marks) at the command prompt.

If Setup referred you to this section and you have neither OS/2 nor a SpeedStor
partition on your computer, see the section "Setup displays the Incompatible
Hard Disk or Device Driver screen" in the "Diagnosing and Solving Problems"
chapter of the MS-DOS User's Guide.

If you do have a SpeedStor partition on your computer, Setup probably referred
you to this section for one of the following reasons:

- Setup could not find in your CONFIG.SYS file a command for the device driver
  that supports your SpeedStor partition. If this is the case, add the command
  line to your CONFIG.SYS file, restart your computer, and run Setup. For more
  information about adding the command line to your CONFIG.SYS file, see your
  SpeedStor documentation.

- Your CONFIG.SYS file has a DEVICE=HARDRIVE.SYS line in it. If this is the
  case, carry out the following procedure:
  1. Use the EXPAND command to expand and copy the SSTOR.SYS file to your hard
     disk. Make sure you copy the SSTOR.SYS file to the same path as the
     HARDRIVE.SYS file. See the PACKING.LST file on Setup Disk 1 for the
     location of the SSTOR.SYS file on the Setup disks and for instructions on
     how to expand and copy it to your hard disk.

  2. Replace the DEVICE=HARDRIVE.SYS command with a DEVICE=SSTOR.SYS command.
     For example, if the command that loaded the HARDRIVE.SYS file was
     DEVICE=C:\SSTOR\HARDRIVE.SYS, you would replace it with
     DEVICE=C:\SSTOR\SSTOR.SYS.

  3. Restart your computer.

  4. Make sure you can access your hard disk.

  5. Run Setup.

1.2 Incompatible Hard Disk or Device Driver:

If Setup referred you to this section, and no other section in this file is
relevant to your system, you have a partition that is incompatible with MS-DOS
6.21. You must delete the partition from your hard disk. See "Using Fdisk to
Configure Your Hard Disk" in the chapter "Diagnosing and Solving Problems" in
the MICROSOFT MS-DOS USER'S GUIDE.

1.3 AT&T 6300 Computer:

If you use an AT&T 6300 computer and your ROM BIOS is version 1.21, contact
your vendor for a ROM BIOS upgrade. The ROM BIOS version number is displayed
when you start your computer.

1.4 Toshiba with a Hard RAM Disk:

These instructions apply to Toshiba models T1200, T1600, T1200XE and T1000LE.

To use the hard RAM disk, carry out the following procedure before you install
MS-DOS 6.21:

1. Back up your hard RAM disk.

2. Using the Toshiba Setup program, delete the hard RAM disk by allocating zero
  kilobytes (KB) to it. All data on the hard RAM disk will be lost.

3. Restart your computer

4. Run MS-DOS Setup.

5. After Setup is complete, run the Toshiba Setup program to reinstall the hard
  RAM disk.

6. Run FDISK, change to drive 2, and create a primary DOS partition. Quit FDISK.

7. Use the FORMAT command to format drive D.

1.5 Tandy with ROM DOS:

Contact your hardware manufacturer for information about upgrading a Tandy
computer with ROM DOS to MS-DOS 6.21. This applies to the following models:
1000EX, 1000HX, 1000SL, 1000SL2, 1000TL, 1000TL2, 1000TL3, 1000RL, 1000RLX,
1000RL-HD, 1000RLX-HD, 1100FD, 2500XL, 2500XL2.

1.6 Setup displays the "Your computer uses a disk-compression
    program that is incompatible with Setup" message.

If Setup indicated that your computer has an incompatible disk-compression
program, you must remove it manually before you can install MS-DOS 6.21. Contact
your disk-compression vendor for an updated version of your software. In most
cases, current versions of disk-compression software are compatible with MS-DOS
6.21.

Alternatively, you can use the procedure below to remove your current
disk-compression software.

1. Back up all the files on your compressed drive. In step 3, you will format
  your uncompressed drive, which destroys all the files on your compressed and
  uncompressed drives.

2. If your Setup disks are compatible with drive A, insert Setup Disk 1 in drive
  A, and restart your computer. After Setup displays the first screen, quit
  Setup by pressing F3 twice.

  If your Setup disks are not compatible with drive A, create a startup floppy
  disk for drive A. To do this, insert Setup Disk 1 in drive B, and a blank
  floppy disk in drive A. Then type "B:SETUP /F " (without the quotation
  marks)at the command prompt.

  When prompted, choose to install MS-DOS on the floppy disk in drive A. After
  Setup is finished, leave the disk in drive A, and restart your computer.

3. At the command prompt, type FORMAT C: /S to reformat your startup drive and
  transfer MS-DOS 6.21 system files to it.

4. Remove the disk from drive A, and restart your computer.

5. Insert Setup Disk 1 in drive A or B, and type "A:SETUP" (without the
  quotation marks) or B:SETUP at the command prompt.

6. After Setup is complete, restore the files you backed up. Do not restore
  older versions of MS-DOS files.

1.7 You deleted files from the directory that Setup needs
   to install the optional Windows programs.

If you typed BUSETUP /E at the command prompt, the "Setup did not find the files
it needs in the directory specified" message appeared, and you think you deleted
the files from your hard disk, insert Setup Disk 1 in drive A or B, and start
Setup by typing "A:SETUP /E" (without the quotation marks) or "B:SETUP /E"
(without the quotation marks) at the command prompt.

1.8 Running Setup if Your Computer Uses Windows NT:

If your computer has Windows NT installed, but does not have MS-DOS installed on
it, carry out Procedure 1. If your computer has Windows NT and MS-DOS installed
on it, carry out Procedure 2.

Procedure 1

1. Run Setup by inserting Setup Disk 1 in drive A and restarting your computer.
  Complete Setup by following the instructions on the screen. When Setup is
  complete, Windows NT will be disabled.

  If Windows NT was installed on a FAT partition, complete steps 2 and 3 of this
  procedure to reenable Windows NT so that you can use both the Windows NT and
  MS-DOS operating systems.

  If Windows NT was installed on a non-FAT partition, see section 1.9.

2. Insert your Windows NT Setup disk in drive A or drive B, and then restart
  your computer.

3. When the Windows NT Setup screen appears, choose Repair, and then insert your
  Windows NT Emergency Repair Disk (which you created when you installed
  Windows NT) to repair the Windows NT system files.

Procedure 2

1. When you start your computer, choose MS-DOS as your operating system.

2. Run Setup by inserting Setup Disk 1 in drive A or B, and typing "A:SETUP"
  (without the quotation marks) or "B:SETUP" (without the quotation marks) at
  the command prompt.

1.9  Setup detects that your computer has a non-MS-DOS
    partition or non-MS-DOS files, and your computer uses
    Windows NT

The procedure you use depends on whether you want to preserve the partition and
its files. Find the section below that describes the configuration you want.

You Don't Want to Preserve the Partition or its Files:

If you don't want to preserve the partition or its files, choose to remove the
partition or files if Setup prompts you to do so. If Setup doesn't offer you
that choice, remove the partition manually after Setup is complete. For
instructions on removing a non-MS-DOS partition manually, see "Using Fdisk to
Configure Your Hard Disk" in the chapter "Diagnosing and Solving Problems" in
the MICROSOFT MS-DOS USER'S GUIDE.

You Don't Want to Preserve the Partition but Want to Save its Files:

If you want to save the data files, but don't want to preserve the partition,
back up the files, run Setup again, and then choose to remove the partition or
files if Setup prompts you to do so. If Setup doesn't offer you this choice,
remove the partition manually after Setup is complete. For instructions on
removing the partition manually, see "Using Fdisk to Configure Your Hard Disk"
in the chapter "Diagnosing and Solving Problems" in the MICROSOFT MS-DOS USER'S
GUIDE.

You Want to Preserve the Partition and Its Files:

Carry out the following procedure.

NOTE If the non-MS-DOS partition takes up all the space on your hard disk, you
must reconfigure your hard disk. You can either let Setup do it for you, as
described in the preceding section, or reconfigure it yourself manually. For
instructions on reconfiguring your hard disk manually, see your Windows NT
documentation.

To install MS-DOS 6.21 and preserve your partition or files:

1. Run MS-DOS Setup.

2. When prompted, choose to continue Setup without removing the partition or
  files.

3. After Setup is complete, insert your Windows NT Setup disk in drive A or
  drive B, and then restart your computer.

4. When the Windows NT Setup screen appears, choose Repair, and then insert your
  Windows NT Emergency Repair Disk (which you created when you installed
  Windows NT) to repair the Windows NT system files.

1.10 Setup displays the "Your computer uses password protection"
    screen.

See section 1.12.

1.11 Setup displays the "Your computer is using an incompatible
    delete-protection program" screen.

See section 1.12.

1.12 Setup detects that your computer uses DR DOS.:

If you have DR DOS installed on your computer, take the following precautions
before restarting Setup:

- If your system has any security features, including password protection,
  disable them. For more information, see "Setup displays the 'Your computer
  uses password protection' screen" in the chapter "Diagnosing and Solving
  Problems" in the MICROSOFT MS-DOS USER'S GUIDE.

  If you have protected any files or directories with a password, remove the
  password protection, particularly if you have protected your CONFIG.SYS or
  AUTOEXEC.BAT files, or your DR DOS directory.

- If you have DELWATCH installed on your computer, carry out the procedure
  "Setup displays the 'Your computer is using an incompatible delete-protection
  program' screen" in the chapter "Diagnosing and Solving Problems" in the
  MICROSOFT MS-DOS USER'S GUIDE.

- If your CONFIG.SYS or AUTOEXEC.BAT files use any conditional commands-- such
  as the "?" or GOTO commands--remove them and adjust the order of commands in
  your startup files accordingly.

- If your CONFIG.SYS file uses the CHAIN command, remove it and adjust the
  order of commands in the file accordingly.

- If your computer uses disk compression, but drive C is not compressed, run
  Setup as described in the chapter "Getting Started" in the MICROSOFT MS-DOS
  USER'S GUIDE. When Setup displays the "Your CONFIG.SYS file contains commands
  that are not valid MS-DOS commands" message, choose the "Modify original
  files" option.

  If drive C is compressed, carry out the following procedure:

  1. Determine which drive is your original uncompressed drive. For more
     information, see your DR DOS documentation.

  2. Make backup copies of the CONFIG.SYS and AUTOEXEC.BAT files on your
     compressed drive, and the DCONFIG.SYS file on your uncompressed drive.

  3. Combine the two configuration files. For example, if drive D is your
     uncompressed drive, type the following at the command prompt:

  " COPY D:\DCONFIG.SYS+C:\CONFIG.SYS D:\CONFIG.SYS " (without the quotation
  marks)

  4. Copy the combined CONFIG.SYS file to drive C. For example, if drive D is
     your uncompressed drive, type the following at the command prompt:

  " COPY D:\CONFIG.SYS C:\CONFIG.SYS " (without the quotation marks)

  5. Copy your AUTOEXEC.BAT to your uncompressed drive. For example, if drive D
     is your uncompressed drive, type the following at the command prompt:

  " COPY C:\AUTOEXEC.BAT D:\AUTOEXEC.BAT " (without the quotation marks)

  6. Run MS-DOS 6.21 Setup.

  7. When Setup displays the "Your CONFIG.SYS file contains commands that are
     not valid MS-DOS commands" message, choose the "Modify original files"
     option.

     When Setup displays the "Because you are currently using the DR DOS
     operating system" message, choose Continue.

  8. After Setup is complete, MS-DOS displays an "Unrecognized command" message
     on your screen for each command in your AUTOEXEC.BAT and CONFIG.SYS files
     that is not a valid MS-DOS command. Remove these commands from your
     CONFIG.SYS and AUTOEXEC.BAT files.

  9. Add the DEVICE=HIMEM.SYS command to the beginning of your CONFIG.SYS file,
     and the restart your computer.

1.13 Installing MS-DOS on a Drive Other Than C:

As described in the following procedure, you can install MS-DOS on a drive other
than C by using the /M switch to copy the system files to your startup drive and
then using the /Q switch to copy your MS-DOS files to a different drive.

NOTE This procedure is designed for advanced users. If your computer uses
disk-compression software, modify the procedure as appropriate.

NOTE If your computer uses disk-partitioning software, such as Disk Manager,
SpeedStor, Priam, or Everex, do not carry out the procedure until you have
carried out steps 1 through 3 of "You need to install MS-DOS manually" in the
chapter "Diagnosing and Solving Problems" in the MICROSOFT MS-DOS USER'S GUIDE.
If your software uses a driver to enable the drive on which you want to install
MS-DOS, make sure you create a startup disk with the driver in a CONFIG.SYS or
AUTOEXEC.BAT file. After you have carried out these steps, skip to step 3 of the
following procedure.

1. Run Setup by inserting Setup Disk 1 in drive A or B, and typing "A:SETUP /M"
  (without the quotation marks) or "B:SETUP /M" (without the quotation marks)
  at the command prompt.

  NOTE Your CONFIG.SYS and AUTOEXEC.BAT files were saved as CONFIG.NEW and
  AUTOEXEC.NEW.

2. Run Setup by inserting Setup Disk 1 in drive A or B, and typing "A:SETUP /Q"
  (without the quotation marks) or "B:SETUP /Q" (without the quotation marks)
  at the command prompt. Follow the instructions on your screen.

3. When Setup displays the system settings screen, choose the MS-DOS Path
  option. Type the drive and directory where you want to install MS-DOS, and
  press ENTER. Continue Setup.

4. After Setup is complete, open your CONFIG.NEW and AUTOEXEC.NEW files and
  ensure that their commands specify the correct path. Save the files as
  CONFIG.SYS and AUTOEXEC.BAT. Then restart your computer.

1.14 Bypassing the Uninstall Disk and Using Default Setup Options:

To keep Setup from creating an Uninstall Disk, use the /G switch with the Setup
command.

To bypass the Uninstall disk and use default Setup options instead of choosing
them yourself, use both the /H and /G switches with the Setup command.

WARNING The primary purpose of the Uninstall disk is to safeguard your files
during and after Setup. If Setup doesn't create an Uninstall disk, you will not
be able to restore your previous version of DOS. If Setup should render your
hard disk inaccessible, you will not be able to use the Uninstall disk to make
it accessible again.

NOTE If you have a version of MS-DOS earlier than 5.0, and you use the /G switch
or the /H and /G switches together, Setup will not prompt you if you need to
update your network files.

1.15 Installing MS-DOS 6.21 on a System with a CorelSCSI UNI_ASP.SYS Driver:

If your system uses the CorelSCSI UNI_ASP.SYS device driver for optical drives,
and Setup stops running when you try to install MS-DOS 6, delete the DEVICE
command in your CONFIG.SYS that loads the Corel UNI_ASP.SYS driver. Then run
Setup again. After Setup is complete, reinstall the Corel UNI_ASP.SYS driver as
you originally installed it. If you continue to have problems, contact Corel
Customer Service.

1.16  Installing MS-DOS 6.21 if you have DrivePro or EZ-Drive:

If your hard disk was set up using Micro House DrivePro(TM) or EZ-Drive(TM), you
must carry out one of the following procedures before you can install MS-DOS
6.21.

- If your DrivePro or EZ-Drive floppy disks include the DOS6INST.EXE file, run
  the DOS6INST program and follow the instructions on the screen. (This program
  is also available on the Micro House BBS at (303) 443-9957.)

- If you don't have the DOS6INST program, run the MHDRIVE program (if you have
  DrivePro) or the EZ-RESET program (if you have EZ-Drive). Press ENTER to
  accept the default answers until the program prompts you to insert MS-DOS
  Setup Disk 1. Insert the disk and then press ENTER. At the second Setup
  screen, choose "Continue Setup and replace your current version of DOS."
  (Note that this procedure will replace your current CONFIG.SYS and
  AUTOEXEC.BAT files with basic versions of these files.)

For additional information, or if you encounter problems, contact Micro House
Technical Support.

1.17 Setup displays the "There is not enough free disk space" screen
    and you are running PC-DOS version 6.1 with compression

If your computer is running PC-DOS version 6.1 with PC-DOS disk compression, when
you run MS-DOS Setup, it displays the message "There is not enough free disk
space on drive C to install MS-DOS."

PC-DOS disk compression is incompatible with MS-DOS. Before you install MS-DOS
6.21, you must first uninstall your PC-DOS disk compression from all your
compressed drives and then completely remove PC-DOS disk compression. For more
information, see "Upgrading from PC-DOS 6.1" later in this file.

Note: If you have completely uninstalled PC-DOS compression and this message
still occurs, you also need to free some space on drive C.

1.18  Setup cannot update a file:

If Setup cannot update one of your MS-DOS files, it displays a message with the
title "Cannot Update File." If you continued Setup, your MS-DOS 6.21
installation is incomplete because the specified file was not updated to version
6.21. If the file is one you know you don't need (for example, if it's a
DoubleSpace file and you don't use DoubleSpace), don't worry about it. (If you
are running PC-DOS 6.1, see section 1.20 of this file). If you are not sure,
update the file using the following procedure (you will need your MS-DOS 6.0
distribution disks):

1. If you use DoubleSpace and the file that was not updated was a DoubleSpace
  file, or if your system does not work properly after you receive this error
  message, insert your Uninstall disk in drive A and type A:\UNINSTAL at the
  command prompt.

2. Insert MS-DOS 6.0 Setup Disk 1 (not MS-DOS 6.21 Setup Disk 1) in drive A or
  drive B, and then use MS-DOS Editor (EDIT) to view the contents of the
  PACKING.LST file. This file tells you where each file is located on your
  MS-DOS 6.0 disks. Determine which MS-DOS 6.0 disk contains the file you need.

3. Insert the appropriate MS-DOS 6 disk in drive A or drive B, and then use the
  EXPAND command to expand the file. For example, to expand the file
  DBLSPACE.BI_ from the disk in drive A to the directory C:\DOS, you would type
  the following command:

  " EXPAND A:\DBLSPACE.BI_ C:\DOS\DBLSPACE.BIN " (without the quotation marks)

  For more information, see the comments at the beginning of the PACKING.LST
  file, or see the MS-DOS 6 User's Guide.

4. Run MS-DOS 6.21 Setup again. This time, Setup should be able to update the
  file.

1.19 Upgrading from PC-DOS 6.1:

If your computer is running PC-DOS version 6.1 with PC-DOS disk compression, you
cannot install MS-DOS 6.21 until you remove the disk compression. This is
because PC-DOS disk compression is incompatible with MS-DOS. Follow these
steps:

1. First, uninstall your PC-DOS disk compression from all your compressed
  drives. (For information on uncompressing PC-DOS compressed drives, see the
  information on the SSUNCOMP command in the PC-DOS documentation.)

2. When SSUNCOMP uncompresses your last compressed drive, it asks if you want to
  disable the driver. Answer Yes to remove the PC-DOS version of the
  DBLSPACE.BIN file.

3. Change to the directory that contains your PC-DOS files, and then type the
  following command:

  " DEL DBLSPACE.* " (without the quotation marks)

4. Insert MS-DOS 6.21 Setup Disk 1 in drive A or drive B, and then type A:SETUP
  or B:SETUP.

Additional query words: msbackup ndw defrag dblguard 6.21

======================================================================
Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS621
Version           : :6.21

=============================================================================

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