my G4 quicksilver Has been having trouble ever since leopard was installed on it. It kernel panics about every couple of hours, sometimes right after a start up. The computer was swapped out for an older computer running 10.4 and the computer is now sitting. I was able to start it up but It would get to the grey screen with the Black Apple Icon and the spinning Startup icon. It would run there for hours until it eventually kernel panic and freeze. While it was running I was able to access the hard drives over the network. We have changed out the ram in an effort to try and narrow down the possibilities and the old ram that was good and is back in. I now cant get the computer to start at all. When I press the power Button all that happens is the fan will com one for about 2-3 seconds and then turn off. Is it the Logic Board? or the Power supply? How can I check? Is it something else?