Using DoubleSpace to Compress a Bootable Hard Card (96517)

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

This article was previously published under Q96517


You should not use DoubleSpace to compress your boot drive if that drive requires a device driver in the CONFIG.SYS file. Because the DoubleSpace driver (DBLSPACE.BIN) is loaded with IO.SYS before the CONFIG.SYS file is processed, Microsoft does not support this configuration.

If you want to use DoubleSpace on such a drive, you should create a new compressed drive using free space on the boot drive. For more information on this procedure see "Using Custom Setup" on pages 121-123 of the "Microsoft MS-DOS 6 User's Guide," or type HELP DBLSPACE /CREATE at the MS-DOS prompt.


If you choose to compress your boot drive (DoubleSpace Express Setup), your computer may not start properly. For example, if drive C is a Plus Hardcard and you compress that drive, DoubleSpace cannot automatically mount the drive on startup and your system may not boot from C. You can either mount the drive from the MS-DOS command prompt or from the AUTOEXEC.BAT. This article outlines the procedures necessary to accomplish this.

Mounting the DoubleSpace Drive from the MS-DOS Command Prompt

You can manually mount the DoubleSpace drive from the command line by using the DBLSPACE /MO command.

Mounting the DoubleSpace Drive from the AUTOEXEC.BAT File

If you want to mount the compressed drive from the AUTOEXEC.BAT file, you must copy the CONFIG.SYS and AUTOEXEC.BAT files to the host drive, copy the device drivers called from those files, and then add a line to the AUTOEXEC.BAT file to mount the compressed drive. To do this, follow the procedure outlined below.

NOTE: This procedure does not work if your drive does not meet the following conditions:
    It is bootable (that is, accessed by the BIOS during the startup process).
    It is a system disk. (If it is not, use the SYS command to transfer the MS-DOS system files.)
To automatically mount the compressed drive:

    Compress the boot drive with DoubleSpace. For example, to compress drive C, type the following at the MS-DOS command prompt:


    Ensure the following files are in the root directory of the host drive (the drive containing the compressed volume file [CVF]):


    To determine which drive is the host drive, type DBLSPACE /LIST at the MS-DOS command prompt.

    Since the files listed above have read-only, hidden, and system file attributes set, use the /A parameter to see the files. To do this, type DIR /A at the MS-DOS command prompt.
    Copy the following three files to the root of the host drive: DBLSPACE.EXE, CONFIG.SYS, and AUTOEXEC.BAT.

    For example, if H is your host drive, you would use the following three commands to copy these files:

    copy c:\dos\dblspace.exe h:\
    copy c:\config.sys h:\
    copy c:\autoexec.bat h:\

    Copy any files called from the CONFIG.SYS file to the host drive. For example, if the command DEVICE=C:\DOS\HIMEM.SYS is in your CONFIG.SYS file, copy HIMEM.SYS to the host drive with the following command:

    copy c:\dos\himem.sys h:\

    Edit the CONFIG.SYS file on the host drive to reflect the new location of the device drivers. Given the above HIMEM.SYS example, change the CONFIG.SYS file on the host drive (H) to read as follows:


    Add the following line to the AUTOEXEC.BAT file on the host drive:


    Any other programs or executable files called from the AUTOEXEC.BAT file should be located on the host drive. If they are not, you need to edit the AUTEXEC.BAT file to reference the correct drive letter. The host and boot drive letters swap when the DBLSPACE /MO line is run from the AUTEOXEC.BAT file.

Modification Type: Major Last Reviewed: 11/26/1999
Keywords: KB96517