Check Disk (chkdsk.exe) is a utility that looks for errors on a hard drive, floppy drive or removable drives. It originated with MS DOS 1.0, and has remained as a command line utility in all MS DOS and Windows versions.

In Windows 95, 98 and ME, Microsoft included Scan Disk, which performed similar functions to Check Disk, but also included a surface scan test. Under Windows NT, 2000, 2003, XP and Vista, a revised version of Check Disk is included that has the ability to check the disk surface for bad sectors, look for lost clusters, cross-linked files, and directory errors.

If your computer tells you that it needs to run Check Disk or you receive frequent Blue Screen Data_Kernel_Inpage_Errors, then you definitely need to act. These errors are usually caused by a hard shut down or a power loss during a read-right operation on that particular drive.

As Check Disk scans your hard, floppy or removable drive, it verifies the integrity of file and folder structures. Sometimes, it can even recover the corrupt data. When you experience a hard drive failure, it is not always the entire hard drive. Often, it may be just certain sectors and in this case, the Operating System should not write to those sectors. Check Disk can be used to scan those sectors and fix them when possible.

To run Check Disk, you will need to:

Open My Computer
Right click on your hard disk (ie: C drive)
Choose properties
Click on the tools tab
Under error checking, click "check now"
Check "automatically fix file system errors" or "scan for and attempt recovery of bad sectors" and let the scan run. This can take quite awhile, depending on the size of your hard drive.

Check Disk may also be ran from system tools or the command prompt in which numerous switches are available. Type chkdsk /? To see a full list of commands with information on each.

The advantages of running Check Disk are innumerable if you are experiencing a disk issue as indicated by the system event logs, blue screen errors or an operating system notification. Otherwise, there is no reason to run this utility.

source: http://www.helium.com/items/841087-the-advantages-of-using-checkdisk