How DoubleSpace Assigns the Host Drive Letter (94336)

The information in this article applies to:
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q94336
This information applies to both Microsoft DoubleSpace and Microsoft DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands and filenames.


When you install Microsoft DoubleSpace, the installation program normally leaves four unassigned drive letters between the last drive and the host drive. For example, if you have two drives (C and D), a RAM drive (E) and a network connection (F), DoubleSpace skips G, H, I, and J, and uses drive K for the host drive.

If DoubleSpace detects Novell NetWare in memory, the host drive is assigned one letter less than the LASTDRIVE command in the CONFIG.SYS file. If that drive letter is unavailable, the host drive is assigned the next available drive letter.

If you install DoubleSpace when device drivers that use drive letters (CD-ROM drivers or RAMDrives) are not loaded or your network software is not loaded, you may need to change the host drive letter.


If you are using MS-DOS 6.2, you can change the host drive letter with the DBLSPACE /HOST command. If you are using Windows and have set up a permanent swap file (PSF) on your host drive, you need to remove the PSF before you change your host drive and then re-create it after you change the host drive. To do this, run Control Panel and choose the 386 Enhanced icon. For more information on re-creating the Windows PSF, see the text in step 10 below. For more information on using the DBLSPACE /HOST command, type "help dblspace /host" (without the quotation marks) at the MS-DOS command prompt and then press ENTER.

If you are running MS-DOS 6.0, you can change the host drive letter by following these steps:

    If you use Microsoft Windows and have a permanent swap file (PSF), run Windows, note the current size of your PSF and change your PSF to None. (You will undo this change later in this procedure.)
    Change to the host drive (for example H).
    Use the ATTRIB command to change the file attribute on the DBLSPACE.INI file. For example:

    attrib h:\dblspace.ini -s -h -r

    Edit the DBLSPACE.INI file with a text editor, such as MS-DOS Editor.
    Change the LastDrive setting to the letter you want to be the host drive.
    Change the first parameter in the ActivateDrive line to the same letter you used in step 5.

    WARNING: Do not change the second parameter (represented by <xx>) in the following example:
           Before change:     ActivateDrive=H,xx
           After change:      ActivateDrive=D,xx
    WARNING: If you use a drive letter that is used by a physical device (such as drive A), for the N value, the system may stop responding (hang) or continually reboot when you restart it.
    Save your changes and quit the text editor.
    Reset the system, hidden, and read-only attributes on the DBLSPACE.INI file. For example:

    attrib h:\dblspace.ini +s +h +r

    Restart your computer (press CTRL+ALT+DEL).
    If you removed your PSF in step 1, run Microsoft Windows and re-create the PSF on your host drive. Do not attempt to create the PSF on your DoubleSpace-compressed drive. You may receive the following message if you re-create your PSF at its previous size:

    Windows will not use more than the virtual memory specified by the Recommended Size. Are you sure you want to create a larger swap file?

    You can ignore this error message; it is likely incorrect. As long as the PSF is not larger than four times your physical memory, Windows can use a swap file that is larger than the recommended size.

Modification Type: Major Last Reviewed: 11/19/1999
Keywords: KB94336