If the computer starts in safe mode try to run a checkdisk on it. Go to "My computer", right click the hard disk, select "Properties", "Tools" and then press "Check now", be sure to tick the box that says "repair errors" or something. If that doesnt work try to select "Last known config"...while the computer is booting...press F8 several times until theres a menu, and then select that option. Tell something if you need something else.