Specs: iMac G5 Intel Core Duo (early 2006). This has been going on for about 2 months at first only occasionally, now everyday. The computer won't power up. When it does, sometimes the DVD spins, but the screen stays black and it just hangs there, other times the speakers crackles horribly and it keeps playing the first sound chime over and over. Other times it starts up ok, then suddenly restarts itself. I've run through all hardware tests it says no trouble is found. I've run through Disk Utility and permissions keep getting rewritten when it restarts, no matter how many times I repair them. I unplug and replug, I've visited all the sites I can for reading up on support, but at this point, I think I might have a power supply issue or logicboard problem... Now it is a crapshoot as to whether it will boot or not, leaning toward not (85% of the time). I have to keep trying to get it going, but then at other times it just dies out and then nada for a while. Does anyone know how I can diagnose and repair without spending a fortune? Since it's not new the warranty has long expired. Thanks.