|try creating a second account, if that works fine, you copy your files from the original account and then delete the original.|
if it fails,
you could after following Fingers advice, run a repair, drop in the win7 repair disk or installation disk, and run repair, that should fix any damaged files.
if all else fails make a backup of all your files and then do a factory restore, or reinstall windows7.
i hate computers!
but cant help myself....