I have a G4 Power Mac. It's the "digital audio" model that has been upgraded with a 1.2Ghz G4 processor. It works well except for one thing. It shuts down randomly and suddenly. Then after 5 or 10 minutes it turns itself back on, reboots and runs fine. (It is set to re-boot after a power failure.) I suspect what is happing is the power supply is turnning itself off due to some kind of a thermal, self protection switch. The fan seems to work but the PS gets warm. What's the cure? Replace the power supply? If so where to get a new(er) one? Will generic PC supplies work.