Drives Inaccessible After Upgrading from Compaq DOS (80890)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    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 Q80890


Compaq technical support has confirmed that extended drives created with FDISK.EXE and ENHDISK.SYS under Compaq's original equipment manufacturer (OEM) version of MS-DOS 3.2 or earlier may be inaccessible after upgrading to MS-DOS 5.0 or later.


The ENHDISK.SYS device driver made it possible to access multiple MS-DOS partitions created by earlier versions of the MS-DOS FDISK utility on fixed disk drives. ENHDISK.SYS was used under Compaq MS-DOS 3.2 and earlier to provide partitioning support for hard disks greater than 32 MB.

ENHDISK.SYS had to be the first device driver installed in the CONFIG.SYS file. This was done to ensure consistency for drive assignments through all the utilities that support partitioned drives created by earlier versions of the FDISK utility.

Compaq technical support recommends backing up the hard drive prior to running MS-DOS 5.0 or later upgrade. If the upgrade has already been performed, and the extended drives are inaccessible, use the MS-DOS UNINSTALL disk to restore the previous version of MS-DOS.

Take the following steps with the old version of MS-DOS installed:
    Back up all necessary data on the hard drive.
    Repartition the hard drive with the MS-DOS 5.0 FDISK command.
    Format all drives on the hard disk. For example:

    format c: /s

    Restore necessary data.
For more information, query on the following words here in the Microsoft Knowledge Base:

combine and fdisk ENHDISK.SYS

For further information contact Compaq technical support.

The Compaq product included here is manufactured by a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB80890