Hopefully someone can help me out with this one, my iMac 24" aluminium just restarted whilst browsing yesterday and hasn't come back on since, just the white/grey screen, no apple logo, no spinning icon, tried the install disk doesn't see it, reset the pram, removed power cable for 10 mins restarted - nothing, slight whirring noise from dvd drive but won't boot, i've even replaced the hard disk in case it was that - nothing... I'm at the end of my ideas now... starting to think it's the logic board looking through various forums... please tell me it's not and it's something simpler! I'm out of warranty and out of cash! please help!!!!!!