Branched from this thread just to save it getting unwieldy and not making sense! I have just got my GPU back from EVGA after RMAing it because it wasn't outputting signal. I've stuck it back in the machine and now it either BSODs at boot or gets into Windows with an unknown device in device manager. I cannot install drivers for the card because the installer doesn't detect any compatable hardware. I have tried with a different card with the same result. Thoughts? Oh, and I'm using a Corsair CX750W PSU