Microsoft KB Archive/99375

= How to Repair a Bad Sector in a Compressed Volume File (CVF) =

Article ID: 99375

Article Last Modified on 11/16/1999

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APPLIES TO


 * Microsoft MS-DOS 6.0 Standard Edition

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This article was previously published under Q99375



SUMMARY
If part of your DoubleSpace-compressed volume file (CVF) occupies a bad sector on the host drive, you may be unable to mount your host drive, or you may receive errors similar to the following:

data error reading drive 

sector not found reading drive 

You can work around this problem by using a third-party surface scan utility (such as Symantec's Norton Utilities Norton Disk Doctor [NDD.EXE] or Central Point Software's DiskFix) or you can use the MS-DOS 6 programs.

NOTE: If you cannot mount your DoubleSpace-compressed drive, contact Microsoft Product Support Services.



Determining If Your CVF Occupies a Bad Sector on the Host Drive
To determine if your CVF occupies a bad sector on the host drive:

 Clear the file attributes on the CVF by typing the following at the MS-DOS prompt and pressing ENTER:

attrib -r -s -h :\dblspace.*

where is the host drive letter.

To determine which drive is the host drive, type dblspace /list (without the quotation marks) at the MS-DOS command prompt and press ENTER. Copy the following files to the host drive (so that you can then unmount it):

COMMAND.COM

DBLSPACE.INF

DBLSPACE.EXE

DBLSPACE.BIN

DBLSPACE.HLP

For example, if your compressed drive is C and your host drive is H, type copy c:\dos\command.com h: at the MS-DOS command prompt and then press ENTER. Unmount the CVF. For example, if your compressed drive is C and your host drive is H, type dblspace /unmount c: at the MS-DOS command prompt and then press ENTER. Copy the CVF to the MS-DOS NUL device. For example, if the CVF is on drive C, type the following at the MS-DOS command prompt and press ENTER:

copy /b c:\dblspace.000 nul

If you encounter a data error reading the file, it indicates a bad sector exists on the host drive.

If you encounter a seek error or a &quot;sector not found&quot; error reading the file, confirm that the CMOS settings for the drive are correct. If the CMOS settings are correct, you most likely have a bad sector on the host drive.

Correcting the Bad Sector with Third-Party Surface Scan Utilities
If the DoubleSpace-compressed drive mounts you can use a third-party surface scan utility to correct the problem:

 Use Microsoft Backup or Microsoft Backup for Windows to back up your data from the compressed drive.</li> Copy the following files to the host drive (so that you can then unmount it):

COMMAND.COM

DBLSPACE.INF

DBLSPACE.EXE

DBLSPACE.BIN

DBLSPACE.HLP

For example, if your compressed drive is C and your host drive is H, type COPY C:\DOS\COMMAND.COM H: at the MS-DOS command prompt and then press ENTER.</li> Unmount the compressed volume file (CVF). For example, if your compressed drive is C and your host drive is H, type dblspace /unmount c: at the MS-DOS command prompt and then press ENTER.</li> Run the third-party surface scan program to correct the bad sector(s).</li> Restart your computer.</li> If the DoubleSpace-compressed drive mounts, run CHKDSK /F to ensure there are no file-allocation errors on the compressed drive. If any files are damaged, restore them from your backups. If the DoubleSpace- compressed drive does not mount, contact Microsoft Product Support Services.</li></ol>

Correcting the Bad Sector with MS-DOS 6 Programs
If the DoubleSpace-compressed drive mounts, you can use MS-DOS 6 programs to correct the problem; however, this process is not as easy as running a third-party surface scan utility.


 * 1) Run SETUP /F to make a Startup disk. For more information, see the &quot;Making a Startup Disk&quot; section in the &quot;User's Guide.&quot;
 * 2) Use Microsoft Backup or Microsoft Backup for Windows to back up the data on your compressed drive.
 * 3) Format the host drive. For example, type format h: /s at the MS-DOS command prompt and then press ENTER.

To determine your host drive, type dblspace /list at the MS-DOS command prompt and then press ENTER.
 * 1) If the bad sector was not on your boot drive, skip to step 7.
 * 2) Put the Startup disk in drive A and restart your computer.
 * 3) Install MS-DOS 6 Upgrade (including the MS-DOS-based version of Microsoft Backup).
 * 4) Run DBLSPACE.EXE to compress your drive.
 * 5) Run MSBACKUP.EXE and perform the compatibility test.
 * 6) Run MSBACKUP.EXE and restore your data.
 * 7) Restart your computer.

Additional query words: 6.00 dblspace double space msbackup mwbackup

Keywords: KB99375

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