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Chkdsk
Run Chkdsk to check the integrity of your hard drive's files, and to repair any errors:
Click to Start/Run and in the run box, type
CHKDSK C: /f
and hit OK. Chkdsk may tell you that it can't check the drive because it's in use; if so, it will offer to check the drive at reboot. Say yes, if so asked.
Repeat for any/all drives or partitions on your system (for example, "CHKDSK D: /f" or "CHKDSK E: /f" and so on. If you were told that would be necessary to reboot to finish checking any drive, reboot now so Chkdsk can run to completion.

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