Picked up a reasonably priced 3 month old XFX 8800gt from a popular aution site. When installed PC won't boot/post. All fans (processor, graphic card and case) all spinning. Hard drive doesn't access and monitor stays on standby. If I put my Galaxy 7900gs back in, everything is OK. Could this be a power problem (vantec 460w), I am currently branching off power from the hard drive supply.