A friend has a 2nd generation Graphite iMac DV (500mhz G3). He's running OS X 10.1 on it.
Recently it began shutting down shortly after start up. If you push the power button on the keyboard you get the "happy" start up chime/bong, the hard drive spins up, the screen changes from black to white, lingers there for 10-20 seconds and then shuts down.
He does think that it might have gotten wet. It was sitting on the floor under an Air Conditioner and there was a small amount of water on top of it. He's let it dry out for over a week now.
Any clues???
Best, Davey O'