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:

    • 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.
    • 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 "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:

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

    • Run SETUP /F to make a Startup disk. For more information, see the "Making a Startup Disk" section in the "User's Guide."
    • Use Microsoft Backup or Microsoft Backup for Windows to back up the data on your compressed drive.
    • 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.
    • If the bad sector was not on your boot drive, skip to step 7.
    • Put the Startup disk in drive A and restart your computer.
    • Install MS-DOS 6 Upgrade (including the MS-DOS-based version of Microsoft Backup).
    • Run DBLSPACE.EXE to compress your drive.
    • Run MSBACKUP.EXE and perform the compatibility test.
    • Run MSBACKUP.EXE and restore your data.
    • Restart your computer.
Modification Type: Major Last Reviewed: 11/16/1999
Keywords: KB99375
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