So my computer was working fine until today, i have put in my new graphics card : geforce 670 gtx zotac amp edition, previously i had 8800 gt. So when i put the gpu in, start the PC and it boots BUT i get no video signal. I made sure i plugged everything right, then i used my old graphics card, and the same thing happend. Could it be unsufficient PSU? Or did my mobo fry somehow? I have also tried switching monitors..