ScanDisk checking drive C:

ScanDisk is a disk checking utility of MS-DOS and Windows 9x. It was introduced in MS-DOS 6 originally as a successor to the CHKDSK utility.

ScanDisk functions by checking the file allocation table, the directory structure and file system of a drive. Optionally, it can also perform a deeper surface scan.

A 32-bit variant is included in Windows 9x as SCANDSKW.EXE, though Windows 95 and 98 also include the DOS counterpart.

ScanDisk also runs automatically after a improper shutdown of Windows 9x. While using the DOS variant in Windows 95 and 98, Windows Me switched to the Windows one, presumably due to the removal of real mode DOS support. It also runs if converting a drive to FAT32, applying DriveSpace disk compression to it or installing Windows 9x (unless the /is is applied to the setup application).

As Windows NT includes a functionally more advanced version of CHKDSK, it was discontinued with the release of Windows XP and was never ported to the NT line of Windows. The disk check during startup was superseded by AUTOCHK.EXE.