Ok, I'm new to this forum as a poster but not as a reader. In fact many of the things that I did to my imac already was because it was an option to try to fix it that members here posted. So on with the problem eh? Originally my iMac G5 (1.6 GHz 17 inch) was failing to boot up. It would get to the grey screen and the apple and it would just stay there and pretend to be a rocket ship with it's little fan whirring as fast as it could after five minutes. So I reset the SMU, fan stopped, still wouldn't boot. Booted it off the 10.5 install cd (which it was running fine until it wouldn't start up). It wouldn't see the Macintosh HD for a while unless you went to disc utility > partitions and changed it from current to one and instead of applying just let it sit there before switching it back to current. Took about 10 minutes of sitting there. I did disk repair said there was no problem. Disk permission repair said there was a few problems and said it repaired them. To be safe I backed everything up using target disk mode (where the fan tried to play rocket again even though I reset the SMU), erased my hard drive and reinstalled. Now it shuts down randomly when it goes idle, and takes 10 minutes to start up past loading the dock to load the apple bar mac hd icon and whatever is on the desktop (which is a single empty folder). I have no clue what the heck is wrong with it as everything I tried led me to a new problem. So there we go... Help?