Try doing a Windows 7 repair.
As your computer starts up press F8 (try it a few times) and Windows should go into safe mode.
Here you have a number of options one of which is repair.
This will try and replace any faulty files with "good" copies
It will not touch your personal files (but best to back them up any way)
More here
http://windows.micros...s-including-safe-mode



