KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q76899: Restoring Boot Partition Boot Sector Using Uninstall

Article: Q76899
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:5.x,6.0,6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 17-DEC-2000

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

- Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
-------------------------------------------------------------------------------

SUMMARY
=======

The primary DOS partition on a hard disk has its own boot sector that contains
information on the format of the partition and the boot strap code. If the
Uninstall program does not complete successfully, this boot sector may not be
restored, which can cause an error message (for example, "non-system disk
error") to be displayed. The primary partition's boot sector can be restored
from the Uninstall disk using Debug.


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

The primary partition boot sector describes the partition format and contains
boot strap code. This sector is the first logical sector on the partition. The
old primary partition's boot sector is stored in the PBOOT.DAT file on the
Uninstall disk. DOS interrupt 26H (absolute disk write) can be used to write
this information back to the first sector of the boot partition.

CAUTION: Use this procedure with caution and only as a last resort. In most
cases, the SYS command is adequate.

To write the old primary partition boot sector back to the first sector of the
boot partition, do the following:

1. Place the Uninstall disk #1 into drive A.

2. Start the Debug program by entering the following at the command prompt:

  " debug a:\pboot.dat" (without the quotation marks)

3. At the hyphen (the Debug prompt), enter the following commands:

  Debug        Command
  Prompt       to Enter           Comments

-            w cs:100 2 0 1     Write pboot.dat (at cs:100) to C;
                                   execute the command at cs:ip.

-            q                  Exit Debug

The boot sector on the primary DOS partition is now replaced by the boot sector
that was there before the MS-DOS 5, 6, or 6.2 Upgrade was installed.

Additional query words: 6.22 5.00 5.00a 6.00 6.20 memmaker

======================================================================
Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version           : MS-DOS:5.x,6.0,6.2,6.21,6.22

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

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.