I have a PowerMac G4 MDD Dual 1.25. After a storm in which I pulled the plug on my Mac when my office's power was going on and off, I began having issues, similar to some other posts, but still different. I'd press the power on button, light would go on only as long as I was pressing it, no chime, no image on screen. I checked web for tips. I cleared PRAM, checked battery, and pulled plug from the wall and reinserted it. It restarted and worked good for a couple of days turning it on and off. Friday am I tried to turn it on, similar problem but different. I'd press power on button, light would stay on as long as I was pressing it. But this time I could hear small fans go on, then after several seconds the main fan would go into high speed mode. I checked web for input. Unplugged unit, checked connections, pulled and reinserted RAM, pressed 'reset PMU', even pulled heat sink off and remove and reseated processors. Unit restarts and worked fine a couple days. Sunday am try to turn it on and it chimes, image on screen, but it locks up in "log on" window. I pull the plug and try to restart it. Same problem as a couple days before. I press on button and light goes off after pressing it with no chime or image on screen, but fan goes on and main fan goes to high speed. Finally try the above steps, with no success until I pull heat sink and remove processor and reseat processor. It works. I'm confused. Could it be a bad power supply even though the fans run? Or is it something else? Any help is appreciated.