most likely a psu problem, probably has bad capacitors if its 5 years old. I read a review about that psu and the capacitors weren't good quality ones anyway. you only need about a 700w psu for that setup if its a good quality one. It would be good if you had another psu to test this. If you want, unplug and remove the psu and open up the cover and look for bulging or leaking capacitors, don't touch anything as they hold a lot of voltage even when unplugged.