Hang or "Read Fault" Accessing Bad Cluster on Compressed Drive (128354)

The information in this article applies to:
    Microsoft Windows 95
    Microsoft MS-DOS operating system 6.0
    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 Q128354


When you are using a real-mode driver (DRVSPACE.BIN or DBLSPACE.BIN) and you try to access a file on a DriveSpace or DoubleSpace compressed drive, the computer stops responding (hangs).

If you are using a protected-mode driver (DRVSPACX.VXD), you receive the error message "Read Fault."

To determine whether you are using a real-mode or protected-mode driver, run DRVSPACE.EXE and click About DriveSpace on the Help menu.


The file that you are trying to access is stored in one or more bad clusters. A bad cluster on a compressed drive is a cluster that cannot be read successfully. Note that an unreadable cluster on a compressed drive does not always indicate a media defect on the physical surface of the disk.


With the protected-mode DriveSpace driver loaded, run ScanDisk for Windows and click the Thorough option button in the Type Of Test box. Test both the system and data areas on the compressed drive, as well as on the host drive. To run ScanDisk and perform a thorough test, follow these steps:
    Click the Start button, point to Programs, point to Accessories, point to System Tools, then click ScanDisk.
    Click the drives you want to test (you should test both the compressed drive and the host drive).
    In the Type Of Test box, click the Thorough option button.
    Click the Options button.
    Click the System And Data Areas option button.
    Click the OK button.
    Click the Start button.


Bad cluster markings due to physical media defects should appear only on uncompressed drives. If ScanDisk is unable to read a cluster on a DriveSpace compressed drive, ScanDisk erases the Microsoft DriveSpace FAT (MDFAT) entry for that cluster and changes the portion of the file that was using the cluster to 0 bytes in length. The physical sectors previously used by the unreadable cluster are marked as free and can be used again.

Modification Type: Major Last Reviewed: 7/28/2001
Keywords: kbDiskMemory KB128354