A power supply can be an easy repair. Usually they are only held in the case by 3 or 4 screws, and clip onto the motherboard into a socket. The power supply socket only goes into the motherboard one way. They can be purchased at Staples, OfficeMax, CompUSA, or Ebay. There are only two basic power supplies AT, and ATX if you have a P2, 3 or 4 then you have an ATX, if it is an older Pentium 1 or mmx then usually is an AT. Now I could be wrong, as I am getting further away from building machines, and my memory is getting bad.