Well... I was playing sro and out of no where my pc restarted.. i thought nothing of it scanned for any viruses and then bam it all started

The moniter went from analog to digital getting no signal from my video card... I have a XFX Gefore 6600 Series and need urgent help.. I tryed reinstalling all my video drivers and nothing it just gets to windows loading screen then looses signal..
Any help would be greatly appreciated