How to Remove a SUBST Drive in MS-DOS 6.22

In MS-DOS 6.22, the SUBST utility allows users to map a file directory path to a virtual drive letter. This guide provides the exact command syntax required to delete or unmount these virtual drive assignments directly from the command prompt.

The Unmount Command Syntax

To remove an existing virtual drive created with the SUBST command, use the /D (delete) parameter with the following syntax:

SUBST drive: /D
  • drive: represents the virtual drive letter you wish to remove, followed by a colon (for example, X:).
  • /D is the deletion switch that instructs MS-DOS to unmount the drive and release the drive letter.

Step-by-Step Instructions

  1. Change the Active Drive: Ensure your current working directory is not on the virtual drive you plan to delete. If you are currently on drive X:, switch to your primary drive by typing C: and pressing Enter.
  2. Identify Mapped Drives: Run SUBST without any parameters to display a list of all currently active virtual drive associations.
  3. Execute the Delete Command: Type SUBST X: /D (replacing X: with the specific letter of the drive you want to remove) and press Enter.
  4. Verify the Removal: Run SUBST once more with no parameters. The previously assigned drive letter will no longer appear in the list, confirming it has been unmounted successfully.