Hook up the old power supply to the unit and leave it connected like you had it before. Ie, whatever fans and such you had connected and disconnected, leave them that way. You want the most minimal amound of devices possible. Motherboard, HDD, ODD, Video card. Leave the side panel off of your case so everything stays cool. Once you do all that stuff start playing some games again. There is a chance that whatever problems you are having could be a result of a DOA power supply. Even with as good a track record as they have some are bound to be DOA.