you need to run chkdisk outside of Windows. Open My Computer. Rightclick on
the hard drive icon C: and go to Properties.
Click the Tools tab - then click the "Check Now" button in the top section.
Check both of the little boxes and press Start.
Windows will tell you that it cannot do this right away, and ask to do it
when you reboot. Say YES. Then click your way out of there and reboot your
machine.