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Q125019: Long Filename Creates an MS-DOS Volume Label

Article: Q125019
Product(s): Windows for Workgroups and Windows NT Networking Issues
Version(s): WinNT:3.5,3.51,4.0;MSDOS:5.0,6.0
Operating System(s): 
Keyword(s): 
Last Modified: 08-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0 
- Microsoft Windows NT Server versions 3.5, 3.51, 4.0 
- Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
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SYMPTOMS
========

After saving a file with a long filename to the root directory of an unlabeled
FAT-formatted drive, you see an unexpected volume label when you reboot under
MS-DOS.

For example, if you save a file as NEWTESTFILE.TXT on a file allocation table
(FAT) partition, Windows NT creates NEWTESTFILE.TXT and NEWTES~1.TXT. If you
boot MS-DOS, the DIR *.TXT command displays:

   Volume in drive C is BX
   Volume Serial Number is 1CC3-3E96
   Directory of C:\ 

  NEWTES~1 TXT        11,438 01-16-95   6:28p
          1 file(s)         11,438 bytes

NOTE: The volume label is BX.

CAUSE
=====

This situation occurs due to the new Windows NT version 3.5 long filename design
for FAT-formatted drives. When you create a long filename under Windows NT, the
FAT file system creates one file but stores both the long filename and short
filename in the directory. One directory entry is used for short file names, and
one or more directory entries are used to store long filenames.

NOTE: For more information on how Windows NT creates short filenames, see article
Q101601 in the Microsoft Knowledge Base.

WORKAROUND
==========

To work around this situation, do not use long filenames when you write files to
the root directory of FAT-formatted drives, or turn off the option to use long
filenames.

To turn off long filename support under Windows NT version 3.5:

WARNING: Using Registry Editor incorrectly can cause serious, system- wide
problems that may require you to reinstall Windows NT to correct them. Microsoft
cannot guarantee that any problems resulting from the use of Registry Editor can
be solved. Use this tool at your own risk.

1. Run Registry Editor (REGEDT32.EXE).

2. From the HKEY_LOCAL_MACHINE subtree, go to the following key:

     SYSTEM\CurrentControlSet\Control\FileSystem

3. Select Win31FileSystem.

4. From the Edit menu choose DWORD.

5. Press 1 and then choose OK.

6. Shutdown and restart Windows NT.

NOTE: Changing this value does not change the file structure.

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

The structure of a MS-DOS entry is:

  Filename:            8 byte
  Extension:           3 byte
  Attribute:           1 byte
  Reserved:           10 byte
  Time:                2 byte
  Date:                2 byte
  Starting cluster:    2 byte
  File Size:           4 byte

The layout of the attribute byte is:

  Bit   Attribute
  ---   --------------
   7    reserved
   6    reserved
   5    archive
   4    sub-directory
   3    volume label
   2    system file
   1    hidden file
   0    read-only file

A dump of the directory structure from the previous NEWTESTFILE.TXT example
shows:

  42 58 00 54 00 00 00 FF - FF FF FF 0F 00 46 FF FF   BX.T...    ..F
  FF FF FF FF FF FF FF FF - FF FF 00 00 FF FF FF FF             ..

  01 4E 00 45 00 57 00 54 - 00 45 00 0F 00 46 53 00   .N.E.W.T.E...FS.
  54 00 46 00 49 00 4C 00 - 45 00 00 00 2E 00 54 00   T.F.I.L.E.....T.

  4E 45 57 54 45 53 7E 31 - 54 58 54 20 00 32 2A 6B   NEWTES~1TXT .2*k
  32 1E 32 1E 00 00 2A 6B - 32 1E F0 0F BA 01 00 00   2 2 ..*k2 =.|...

The NEWTES~1.TXT entry attribute byte is 20 (hexadecimal), indicating a file with
just the archive bit set. Both entries for NEWTESTFILE.TXT have the attribute
byte set to 0F (hexadecimal), indicating a read-only, system, hidden file, and a
volume label. This combination is not expected in the MS- DOS environment.

Additional query words: 5.00 5.00a 6.00 6.20 6.21 6.22 prodnt msdos hex hexa upper lower mixed lfn file name names

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Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT350search kbWinNT400search kbWinNTW350 kbWinNTW350search kbWinNTW351search kbWinNTW351 kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS350 kbWinNTS351search kbWinNTS350search kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version           : WinNT:3.5,3.51,4.0;MSDOS:5.0,6.0

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

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