Hi, I have an iMac 27" Late 2009 that got it's Seagate HDD replaced by Apple 6 months ago (replacement program). However, the HDD Fan ramps up to the full speed (5500RPM) for no reason. This happens very random (say 10 minutes of using from a cold boot). The Hard Drive sensor functions and it runs cool (40 degrees centigrade). Why does it still go to full speed even though it measures the right temperature for the HD? I tried a clean install, smc and pram reset. Advise or suggestions would be greatly appreciated!