I'm not saying you should do this, but I figured out how to upgrade the hard drive in the new iMacs to one of a different manufacturer. My i7 came with a 1TB Seagate. I now have a 2TB Hitachi in there. All I had to do to get the thermal sensor to work is cut off the part of the connector on the thermal sensor cable that didn't have wires attached to the pin outs, then fit it on to the new one. At first, the fan ran at full speed. It would start at about 2500 and slowly creep up to 5500. I just flipped the cable over and the fan runs at 1200 rpm now. The Hitachi so way quieter than the Seagate. I thought people were exaggerating when they complained about hard drive noise, it really is loud and it sounded like my iMac was really hungry and its stomach was growling.