DIR and CHKDSK Report Different Amounts of Free Space (96825)

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 Q96825
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.


Delete Sentry increases the amount of free space that MS-DOS reports (through interrupt 21h function 36h) to programs by the size of all deleted files stored in the hidden SENTRY directory. This affects the amount of free space reported by the DIR command, Windows File Manager, and many other programs.

To determine the amount of disk space that is actually free, run CHKDSK and look at the "bytes available on disk" value. CHKDSK correctly determines the disk free space because it bypasses Delete Sentry and examines the MS-DOS file allocation table (FAT) directly.

To determine how much disk space is free if all Delete Sentry files are purged, use the DIR command.


Delete Sentry automatically purges deleted files if more disk space is required. For more information, see "Purging Files Protected by Delete Sentry" in the "Managing Your System" chapter of the "Microsoft MS-DOS User's Guide" for version 6 or 6.2.

Delete Sentry may increase the disk free space on DoubleSpace drives by too little if the data being added to the drive is less compressible than the data being purged from the hidden SENTRY directory.

Modification Type: Major Last Reviewed: 11/19/1999
Keywords: KB96825