After transitioning from OS X to Vista I ran into some cooling problems. Under OS X I can use SMC Fan Control to adjust the rear fan speed, in order to cool the memory banks. Under Vista I could not find such a tool - Input Remapper constantly blue screened my Mac Pro, so that didn't last long at all. So I decided to do some tinkering around inside:

http://marokero.com/gtx295/ND3_0085.jpg
http://marokero.com/gtx295/ND3_0086.jpg
http://marokero.com/gtx295/ND3_0088.jpg
http://marokero.com/gtx295/ND3_0087.jpg

I put a SilverStone FM121 and routed the wires around the case, and installed the fan speed potentiometer in the rear. Temps are much lower now. Now I can safely crunch for MW and I no longer worry about frying my Mac Pro. ;)

If you have booted into Mac OS X with SMCFanControl on your desired fan speeds, won't a direct reboot (by restarting, without shutting down the MP) into Windows actually maintain the speed of the fans as per SMCFanControl settings...?

Yes, that used to work until I got the GTX 295 installed. Now I don't boot into OS X unless I first change graphic cards and really desperately need to use Aperture instead of Lightroom.