Ok my second replacement iMac has just arrived. I am fairly sure the display is faulty (again) because it just doesn't look white. And secondly yet again I have the issue where something inside (fan?) seems to whir up and won't shut up. Now I am fairly sure I am going to send it back just because of the screen but what I want to know is if the whirring sound is normal. If I put the iMac to sleep and turn it back on then it whirs up again and hums, you can hear it whirring up it is quite noisy. Can anyone else with an i7 iMac hear this when they take it out of sleep? I have always thought that it would be dead silent.