So my iMac 17inch (core 2 duo 2.00ghz 1 gb ram) shut off randomly today. its had overheating problems in the last while so i downloaded a fancontroller and up'd the fan speed a little bit. But today, it turned off and never turned back on. The hard drive span for a second and the screen flickered but it turned off again. Its been like this for HOURS now. Whats wrong? I would really have to see the thing go.