Click Start, select Run.

In the box, type cmd and click Ok. In the black DOS window, type: chkdsk c: /f (The /f command automatically fixes any errors encountered.
Go to Start, Shutdown, and restart the computer. When the computer restarts, it will run chkdsk automatically. The Check Disk process could take over an hour, so schedule this when you have something else non-computer related to do. On rebooting the PC, you will see a window that shows the progress of the disk check. When it's finished,, it will boot back to the normal version of Windows.
Disclaimer included below. Opening your computer case could void your warranty, and expose you to possible electric shock. Please be careful.