Ok, I stripped down the computer to just the psu, motherboard, and cpu, but I still have the same problem - which is that when I turn on the psu, the heatsink fan turns on. I noticed that if I have the 4-pin power plugged into the mbd as well as the 24 pin power that the fan will start then stop after about 2 seconds. I'm not really sure why the fan would even start if never hit the power button. I did reset the CMOS battery by pulling it out and then waiting a couple minutes, then I put it back in. I just didn't know if there was some way to figure out if the problem is the mobo or the cpu without replacing one or the other. Thanks.