|Try to start it in safe mode. Power off then power on and press F8 key after POST stuff. If works then try to use system restore point. (NOT the DVD's it is a Microsoft program to go back in time when it worked)|
If not then might have to use your Vista DVD (or anyone's if similar version) and try booting to DVD. Then select "repair"
Playing to the angels
Les Paul (1915-2009)