That'll be a screwed Windows install. Best bet is to wipe & reinstall.
There's a tiny chance you could repair the install, but I wouldn't bet on it. If you want to give it a go do the following:
Click start
Type CMD in the search box
When it finds it right click CMD & select "run as administrator"
Once you have a command prompt run the command SFC /SCANNOW
Keep in mind there's a good chance it wont fix it, and depending on your luck could make the problem worse. I'd just back up stuff & reinstall.