Hi Tom,
This blue screen is called Blue Screen Of Death and has been implemented by Microsoft to prevent any damage to your computer. The problem you describe is a little bit confusing. Did you try system restore (windows based), or system restore (dos based) Did u also try restarting in safe mode?? Have u installed any software or driver recently?? If you can check the code written on the BSOD, it will be helpful. it's an asci code like 000x00032442 etc... Please let us know so we can go from there.
Cheers