Since I am running Intel's D845BG MotherBoard which has Intels SMBus and Intel developed a very nice monitoring application called Intel Active Monitor. It tells you all of your Processor Core Voltages, PSU Voltages, System Zone and CPU Core temps and supports up to 2 fans (the board only supports RPM readings on 2 of the 3 pin connections). I have swapped fans around a hundred times before, when I installed my new CoolerMaster Fujiyama Heat Pipe HSF it had a 2500 RPM silent fan and it ran alot cooler than my old HSF but I still wanted more. So I took the 6000 RPM 46 CFM fan off my old HSF and bolted it onto the new HSF. When I plugged it in I also did some other tinkering. I removed my GeForce 3 Ti200 Card and my Wilamette's heat sink. I tore the HSF off the GeForce and cleaned the core and HSF and applied Arctic Silver II and did the same with the Wilamette Heat Sink and reinstalled everything. When I booted the system back up I got an error on Active Monitor that said one of my fans had reached 0 RPM yet all of my fans were (are) working. I read through the Intel documentation and it says that occasionaly when you change fans you may have to reinstall Active Monitor. So I did that assuming it would remedy the problem. No such luck. I have only one fan showing in Active Monitor now. I did remove the 3 pin connector from the fan so that I could get expandable nylon and heat shrink onto the wires but I made damn sure that I have the wires proper orientation noted. I also made certain that the connectors were installed back into the clip right side up and that they would make contact with the pins on the mobo. Still no luck. I guess my best bet is to plug another fan into that port and move the CPU fan to the other port and see what happens.