Two ways: 1) open My Computer, right-click on the hard drive, select
Properties, then the Tools tab, and click Check Now.  Check the
"Automatically fix file system errors" and click Start.  When you're asked
if you want to perform the operation the next time you boot, click Yes and
reboot.  2) click Start>Run and enter "chkdsk /f" (without the quotes, but
with the space) in the Open field.  Click OK.  You'll be asked if you want
to perform the check when the system boots.  Enter Y and reboot.