I bought a gtx660 and when fitted I can't get past splash screen. My system runs fine with my old VGA in it (pny quadro 600). System specs are- asus m5a99x evo mobo, amd fx8120 black edition, Kingston hyperx ram 16 gb, ocz 240gb ssd, seagate 2tb, corsair 750w psu new. I've never had a problem with the system before now. Thanks in advance.