I have been messing around with my 20" iMac for about three hours now and it simply blows... literally. I restarted it three hours ago and ever since, I only can get to the white screen with the apple logo, and then after two minutes the fans start up on full power (like a 747 is getting ready for take-off) and it stays like that for at least five minutes to where my patience run out and I turn it off (for as much as 30 minutes) then try booting it again. Same thing! Any suggestions on what to do? WOWOWOW! Talk about a coincidence.... I think my iMac sitting on the desk behind me saw me writing this and decided to work. Now it's waiting for my password at login. So I guess it works now, but what was wrong and what do I do if it happens again????