Microsoft KB Archive/174865

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Compressed Read-Only Drive Not Mounted at Startup


The information in this article applies to:

  • Microsoft Windows 95 OEM Service Release, versions 2, 2.1


If Windows 95 OEM Service Release 2 (OSR2) is installed on or configured to boot from a compressed drive, the compressed volume may not be mounted and Windows may not start if the drive is read-only. This may occur with removable disks such as floppy disks which can be write-protected.


The real-mode DriveSpace driver (Drvspace.bin) does not mount a compressed volume on a read-only drive.


This functionality is provided by the following updated file for Windows 95 OSR2 and OSR 2.1, and later versions of this file:

   DRVSPACE.BIN  version 4.40.1112  dated 10/23/97  65,303 bytes 


Microsoft has confirmed this to be a design limitation of Microsoft Windows 95 OEM Service Release 2 (OSR2). An update to address this limitation is now available for OSR2 and OSR 2.1 only, but is not fully regression tested and should be applied only to computers experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft does not recommend implementing this update at this time. Contact Microsoft Technical Support for additional information about the availability of this update.

This issue is resolved in Microsoft Windows 98.


For additional information, please see the following articles in the Microsoft Knowledge Base:

Q96200 DoubleSpace Cannot Mount Compressed Write-Protected Disk

Q137001 Automatic Mounting in Real Mode Disabled in DriveSpace 3

For additional information about Windows 95 updates, please see the following article in the Microsoft Knowledge Base:

Q161020 Implementing Windows 95 Updates

Additional query words: boot

Keywords : kbenv osr2
Issue type : kbprb
Technology : kbWin95search kbOPKSearch kbWin95OPKOSR2 kbWin95OPKOSR210

Last Reviewed: January 31, 2001
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