Uninstalling Older Version of MS-DOS Without Uninstall Disk (76882)

WORKAROUND

The procedures below allow you to restore the previous version of MS-DOS.

NOTE: If you are using an original equipment manufacturer (OEM) version of MS-DOS, contact the OEM for the correct uninstall procedure.

Reinstalling MS-DOS Version 4.0 or 4.01

To reinstall MS-DOS version 4.0 or 4.01, do the following:

1. If you are using DoubleSpace or DriveSpace, you must first remove it before you install an earlier version of MS-DOS.
2. Boot the machine with an MS-DOS 4.0 or 4.01 boot disk.
3. At the drive A prompt, type the following command and press ENTER:

   sys c:

4. With an MS-DOS 4.0 or 4.01 boot disk in drive A, type the following command and press ENTER:

   copy a:\command.com c:\

5. Delete all MS-DOS 5.0 or later files from the DOS directory. Make sure you save or relocate files that are not related to MS-DOS.
6. Copy all the MS-DOS 4.0 (or 4.01) disks into the DOS subdirectory on the hard disk drive.
7. Remove or replace commands in the AUTOEXEC.BAT and CONFIG.SYS files that are not supported by MS-DOS 4.0x (DEVICEHIGH, LOADHIGH, DOS=HIGH, and so forth).
8. Remove the disk from the floppy disk drive and reboot the computer.

Reinstalling MS-DOS Version 5.0 or 5.0a

To reinstall MS-DOS version 5.0 or 5.0a, do the following:

1. If you are using DoubleSpace or DriveSpace, you must first remove it before you can install an earlier version of MS-DOS.
2. Run Setup with the /F parameter to create a working set of MS-DOS 5.0 disks with expanded files.
3. Boot the machine with an MS-DOS 5.0 boot disk, such as the startup disk created in step 2.
4. Use the SYS command to transfer the MS-DOS system files to drive C. For example, type sys a: c: and then press ENTER.
5. Delete all MS-DOS 6.0 or later files from the DOS directory. Make sure you save or relocate files that are not related to MS-DOS.
6. Copy all the MS-DOS 5.0 (or 5.0a) files from the disks created in step 2 into the DOS directory on the hard disk drive.
7. Remove or replace commands in the AUTOEXEC.BAT and CONFIG.SYS files that are not supported by MS-DOS 5.0. (For example, DEVICEHIGH and LOADHIGH in MS-DOS 5.0 do not support the /L and /S statements, EMM386.EXE does not support the HIGHSCAN parameter, and so on.)
8. Remove the disk from the floppy disk drive and reboot the computer.

Reinstalling MS-DOS Version 6.0, 6.2, or 6.21

If you are currently using MS-DOS 6.22 DriveSpace, you must remove DriveSpace before proceeding. If you already installed the earlier version of MS-DOS, you no longer have access to your DriveSpace-compressed drive. To have access to this information, you must reinstall MS-DOS 6.22, remove DriveSpace, and then proceed with the following procedure.

To reinstall MS-DOS version 6.0, 6.2, or 6.21, do the following:

1. Run Setup with the /F parameter to create a single startup floppy that contains system files from the version of MS-DOS you are installing.
2. Boot from the startup disk.
3. Delete all MS-DOS files from the current MS-DOS directory.
   
   NOTE: Be sure to save any files that are not related to MS-DOS (for example, document files that you may have created and saved into the MS-DOS directory).
4. Remove or replace commands in the AUTOEXEC.BAT and CONFIG.SYS files that are not supported by the version of MS-DOS you are installing. (For example, HIMEM.SYS in MS-DOS 6.0 does not support the /TESTMEM parameter.)
5. Reinstall MS-DOS by running setup from Setup Disk 1.
   
   NOTE: To reinstall MS-DOS 6.2x Step-Up, you must reinstall the version of MS-DOS that was on the system prior to MS-DOS 6.2.

Alternative Procedure

Alternatively, you can reinstall the desired MS-DOS version using the installation procedure documented with your specific MS-DOS "User's Guide."

For more information about manually installing MS-DOS, query on the following words in the Microsoft Knowledge Base: