Q101061: CHKDSK Reports "Probable Non-DOS Disk"
Article: Q101061
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:6.0
Operating System(s):
Keyword(s):
Last Modified: 19-NOV-1999
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The information in this article applies to:
- Microsoft MS-DOS operating system version 6.0
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SUMMARY
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When you run CHKDSK on a logical MS-DOS or DoubleSpace-compressed drive, you may
receive the following error message if the drive was not partitioned or
formatted with MS-DOS utilities, or if the media descriptor byte in the file
allocation table (FAT) for the drive is incorrect or corrupted:
Probable non-DOS disk
Continue (Y/N)?
MORE INFORMATION
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This error message may occur for one of the following reasons:
- The disk was not formatted with the MS-DOS FORMAT command or was partitioned
using a nonstandard partitioning scheme. The CHKDSK command should be used
only on MS-DOS disks. Confirm that the disk or drive is an MS-DOS disk and
that it is formatted.
Some disks not formatted with the MS-DOS FORMAT command may cause the CHKDSK
command to display this message; however, the CHKDSK process may still
function properly. If you have a nonstandard partitioning scheme, make sure
the correct device drivers are loaded.
- The media descriptor byte in one or both of the file allocation tables (FATs)
for the drive producing the error message is incorrect or corrupted.
If the drive has been partitioned and formatted with MS-DOS, you can use a
disk editor (such a Norton DiskEdit) to edit the FAT. The FAT should be
viewed as hexidecimal. The first byte in the FAT for a hard (fixed) disk
should be "F8" (without the quotation marks). The following is an example of
the first three lines of the FAT and the location of the media descriptor
byte:
00000000: F8 FF FF FF 03 00 04 00 - 05 00 06 00 07 00 08 00
00000010: 09 00 0A 00 0B 00 0C 00 - 0D 00 0E 00 0F 00 10 00
00000020: 11 00 12 00 13 00 14 00 - 15 00 FF FF 17 00 18 00
WARNING: The above text is an example. You should NOT use a disk editor to
change your FAT to match the above text.
The media descriptor byte is the first two digits after the colon (:) in the
first line, in this example. "F8." This is the correct setting for all MS-DOS
formatted fixed disks (hard disk drives). Below is an abridged list of valid
entries for the media descriptor byte and the media type the descriptor
denotes:
F8 Fixed disk
F0 3.5-inch, 2-sided, 18-sector
F9 3.5-inch, 2-sided, 9-sector
F9 5.25-inch, 2-sided, 15-sector
FC 5.25-inch, 1-sided, 9-sector
FD 5.25-inch, 2-sided, 9-sector
FE 5.25-inch, 1-sided, 8-sector
FF 5.25-inch, 2-sided, 8-sector
FE 8-inch, 1-sided, single-density
FD 8-inch, 2-sided, single-density
FE 8-inch, 2-sided, double-density
FD 8-inch, 2-sided, double-density
REFERENCES
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"The MS-DOS Encyclopedia," Microsoft Press, 1988
Additional query words: dblspace 6.00 nondos
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Keywords :
Technology : kbMSDOSSearch kbMSDOS600
Version : MS-DOS:6.0
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