SCANDISK

Starts Microsoft ScanDisk, a disk analysis and repair tool that 
checks a drive for errors and corrects any problems that it 
finds. ScanDisk is a full-featured disk analysis and repair 
program. It is designed to work on both uncompressed drives and 
compressed drives.

Note: SCANDISK.EXE is for MS-DOS. For Windows 9x, use 
SCANDSKW.EXE instead. For Windows NT/2000, when you want to check 
the disk for errors, right click on the icon of the drive you want to 
check, then select "properties", turn to "Tools" page. 
There you can check the drive by click "Check for errors of the 
disk". Important: Do not use SCANDISK.EXE for MS-DOS versions 
from 5.0 to 6.22 to check a disk formatted and maintained by 
Windows 9x or Windows NT/2000. To check a Windows 9x disk, you 
can run SCANDSKW.EXE from Windows or run SCANDISK.EXE from 
the startup disk.

Usually, there is no need to check the disk for errors. Only 
when you run an illegal program or when the system crashes, or 
when you turned off the computer without quitting Windows, 
you need to check the disk. But for some 
unforeseeable errors, you'd better check the disk regularly, at 
least once a month.

There are also third party tools to check disk integrity for 
you, such as Norton Disk Doctor. Some of them are very good, but 
I think Microsoft ScanDisk is adequate in most situations.

ScanDisk can check both logical errors and physical errors of a 
disk. It checks Partition Tables, Boot Sector, Media Discriptor 
(which contains disk specifications), Directory Structure and 
File System one by one. You can choose whether to scan disk 
surface. Checking the surface of the disk can tell you physical 
errors of the disk.

For more information, please refer to MS-DOS Help or Windows NT 
command line command help.