You can test disk drives for problems and errors with the Chkdsk.exe program. It runs from the command line or from the Windows GUI. Check Now shows up before Defragmentation and Backup in the Windows disk Tools menu for a reason: Check your drive for errors first before you perform a defrag or a backup!

Automatically fixing file system errors with recovery attempts of bad sectors also is a Chkdsk option. If you decide to automatically fix file system errors, Chkdsk will be set to run at the next restart, required since Chkdsk needs sole access to the drive. Chkdsk performs a three-phase test of the drive after the system is rebooted but before the desktop appears.

You can also run Chkdsk from the command prompt. For options, type Chkdsk /? from the command prompt.

In Vista, you will need to run this command in elevated mode:

    • Start |All Programs | Accessories | Command Prompt | Right-click Command Prompt | select Run as Administrator | Click Continue at the permission window.

    • Start | type cmd | press Ctrl+Shift+Enter to execute cmd.exe in elevated mode | Click Continue at the permission window.

If a drive is 'dirty' (has errors), Chkdsk launches automatically at boot up; to change this, run Chkdsk with with  options from the command prompt, and chkdsk /?  from a command prompt shows you the choices.