Make sure you back EVERYTHING up first, that means, Fonts, Address Books, Favorites, Documents, and all saved data. You will have to reinstall all of your software afterwards.
Omg thanks ! you saved my computers life ! But I didn't back up my drive because my Local disk is corrupted. I noticed that when I was in system repair , my partition size was 0.
So now I'm typing this in a formatted clean installed windows 7 ultimate computer.