Just to be on the safe side, i would go to newegg, purchase yourself a 60 dollar 500 - 550 watt psu (preferrably a known name brand) and see if that helps your problem. If it doesnt, you just future proofed your computer for newer drives that may cause power issues later. If it does fix your computer then your a happy man.
Edit: Make sure that PSU has Dual 12v Rails (helps a lot)