ScanDisk Marks Valid Clusters Bad with Incorrect CMOS Settings (119429)

The information in this article applies to:
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q119429


When you perform a surface scan with ScanDisk, some valid, usable clusters are designated as bad (unusable).


This problem occurs if your CMOS settings are set incorrectly for your hard disk drive. For example, if you have a 150-megabyte (MB) hard disk and the CMOS is set for a 20-MB hard disk, ScanDisk scans the first 20 MB correctly, but the remaining 130 MB are mark as bad.


To correct your cluster entries:

    Back up your files.
    Correct your CMOS settings. (For more information, contact your hardware vendor.)
    Run FORMAT /C /S to reformat the drive. (The /C parameter tells FORMAT to reexamine each cluster, and the /S parameter makes the drive bootable.)

    NOTE: Use the /S parameter only if the hard disk is your C drive.
    Reinstall MS-DOS and Microsoft Backup.
    Restore your data.


Running ScanDisk after you correct the CMOS settings does not correct the problem. To avoid corrupting protection schemes that mark clusters bad, ScanDisk does not change usable clusters marked as bad back to good.

Modification Type: Major Last Reviewed: 11/20/1999
Keywords: KB119429