My imac (G4 flat panel) will not boot up. When I press the power buttom the display light comes on, but that is it. Sometimes the Hard drive will start to spin up and I get the gray screen, then nothing. Three days ago, everything was fine, and then the imac started freezing up. I would restart it, and it would work again for 15-20 minutes - then freeze. Now, I can't get it to do anything except an occasional gray screen. I am not sure if it is the hard drive (can't really hear it spinning up or if it is the motherboard. Does anyone have an idea? If I took it to an Apple store would they look at it and give me a dignosis for free? Or would I have to pay them to look at it? Any help here would be appreciative.