I recently got my display and HDD replaced under AppleCare. After my iMac was returned to me, it made a whirring noise which was very noticeable in a room with little ambient noise. It was essentially silent prior to the repairs. I sent it back to the AASP, who claim (a) they couldn't hear anything and (b) nothing awry was evident in the diagnostics. I then phoned Support who arranged for it to be sent by courier to another AASP. They also claimed to not hear the noise. I have since identified the noise to be due to the fan, using SMC Fan Control - the whirring gets louder and faster as I increase fan rpm. This noise starts as soon as I boot the machine (before the Apple logo), my temperatures are fine and my fan speed is normal (around 800rpm). My nearest Apple store is 2 hours away by public transport and I do not have access to a car. I think the only way I'll be able to draw attention to the problem is to go with my iMac and make them compare it to a machine in-store. Has anyone else had a similar problem? Any reccomendations for how to get this fixed once and for all?