How to Repair a Bad Sector in a Compressed Volume File (CVF) (99375)


The information in this article applies to:

  • Microsoft MS-DOS operating system 6.0
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 <x>
sector not found reading drive <x>
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.

MORE INFORMATION

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:

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

    attrib -r -s -h <drive>:\dblspace.*

    where <drive> 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.
  2. 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.
  3. 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.
  4. 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 "sector not found" 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:

  1. Use Microsoft Backup or Microsoft Backup for Windows to back up your data from the compressed drive.
  2. 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.
  3. 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.
  4. Run the third-party surface scan program to correct the bad sector(s).
  5. Restart your computer.
  6. 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.

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 "Making a Startup Disk" section in the "User's Guide."
  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.
  4. If the bad sector was not on your boot drive, skip to step 7.
  5. Put the Startup disk in drive A and restart your computer.
  6. Install MS-DOS 6 Upgrade (including the MS-DOS-based version of Microsoft Backup).
  7. Run DBLSPACE.EXE to compress your drive.
  8. Run MSBACKUP.EXE and perform the compatibility test.
  9. Run MSBACKUP.EXE and restore your data.
  10. Restart your computer.
Modification Type:MajorLast Reviewed:11/16/1999
Keywords:KB99375
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