I just returned my iMac because of a few dead pixels. Got a new one. Looks great. But now I notcie that if you touch the back of the iMac, it has a slight vibration to it. It's slight, but it's there. If this were my first iMac, I would assume that this is normal. But I don't remember feeling that vibration on my previous iMac. It is possible that it was there and I never noticed it because I was too fixated on the dead pixels, but I just want to make sure. So, iMac owners, if you touch the back of your iMac - say near the top or middle - is there a slight vibration? I am assuming that this is the hard drive or fan, but I want to make sure that mine isn't faulty. Any help would be great. Please provide me with some peace of mind OR a reason to go back to the store.