Please run (from an admin dos prompt)
sfc /scannow
and
chkdsk /r
I would be interested to know if chkdsk discovers any bad blocks...also, based on those events, look for something in device manager like "unknown device" or something with an exclamation point next to it. If there is something like that, rt-click on it, go to properties > Details > and post the value string under the "device instance ID" drop down selection.
