I recently found a maxed out 21.5" 2010 iMac for a good price. Got it home, and everything seems to work fine. But for some reason the fans run really loudly upon startup. I put the computer to sleep, and when it woke up, it was silent. Ran for about 30 seconds, then got loud again. Went to sleep and woke up again. Now there is no fan noise at all. I tried watching HD videos, playing games on maxed out settings, and doing stress tests and the fan is very quiet, nearly silent during operation. So I restarted the computer. Did the same thing. Put to sleep and woke up a few times and it was fine. At this point I decided it would be a good idea to reset the SMC. I did that, and still nothing. This really makes no sense to me, it's silent during heavy operations, and doesn't get burning hot, but the fans rev up to 100% when I start it up.