Using DiskLock PC with MS-DOS 5.x or 6.x (73444)

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

This article was previously published under Q73444


This article contains information about using DiskLock PC versions 1.01 and 1.02 from Fifth Generation Systems with MS-DOS version 5.0 or 6.0.

DiskLock is drive-locking software. Once installed, it modifies the master boot record and installs the device driver, DISKLOCK.SYS, in the CONFIG.SYS file. According to Fifth Generation Systems, DiskLock PC is compatible with MS-DOS 5.0 or 6.0 as long as CONFIG.SYS contains the following lines:


If either of these lines is not present, DiskLock PC may not load or may generate a series of error messages.

According to Fifth Generation Systems, the recommended steps to install MS-DOS 5.x or 6.x on a machine with DiskLock PC are:
    Uninstall DiskLock.
    Install MS-DOS 5.0 or 6.0.
    Install DiskLock.


DiskLock PC allows locking of floppy drives, individual partitions on a hard drive, files, and directories.

DiskLock PC modifies the master boot record so that the first thing the system does is look for the DISKLOCK.SYS device driver. If such a driver cannot be loaded, the machine is unusable. You may be able to access the drive(s); however, all data on the drive(s) or locked files or directories is encrypted. To verify whether you can properly access the drive, issue the DIR command. The screen displays scrambled information that cannot be read. This is due to the encrypting in effect by DiskLock. No data is lost, however, and the hard drive is still operable as long as you load DiskLock again.

If you use FDISK to view the partition(s) information, the locked drive will show as a XENIX partition. Even though such a partition can be deleted in MS-DOS 5.0 or 6.0, doing so is not recommended because your data is still encrypted and you cannot access it.

Loading MS-DOS low or falling to install HIMEM renders the machine unusable. If you cannot reload DiskLock, the only way to be able to use the hard drive is to low-level format it. If DiskLock hangs during installation after installing MS-DOS 5.0 or 6.0, you cannot use it.

If you use DiskLock PC with MS-DOS 6.0, you cannot use the MEM command to display what is loading in the Upper Memory Block (UMB) area. Upper memory is displayed as 0. DiskLock does not prevent the use of the UMB; it just prevents the information from being shown when you issue the MEM command.

DiskLock PC is manufactured by Fifth Generation Systems, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Modification Type: Major Last Reviewed: 11/25/2003
Keywords: KB73444