I agree with everyone here....most likely power supply. If you have a multimeter, there are online guides that are very simple that you can test your rails(pins on the 24 pin adaptor). It's easy, cheap and accurate plus costs no money, only the pain of unplugging. Power supplies are finicky little @%$#s. Generally, I take an easier yet slightly more expensive track.....I always have a backup power supply so if I'm questioning the ps, I'll just swap out and run the rig with the replacement until I take time to test the potentially faulty supply.