I got a second hand GPU from a friend, so I took my old GPU out of my PC ready to put the new one in. But I realised I don't have a cable to connect it to the power supply as my old GPU didn't require one. So I put my old GPU back in, not touching anything else at all. Then I came to turn my PC on, after making sure everything was as it was before, and absolutely nothing happens whatsoever. No fans turn on and nor do any LEDs, I think this must be a problem with the power suply, however I posted this in the G&D forum because the only thing I did was remove and replace my GPU.