QUOTE(TheBigB @ May 6 2011, 06:05 PM)
I can't help you and say where to put it, but I have to warn you that if you happen to put it in a really bad place, it can in fact make the cooling worse than without it.
LOL that sounds ominous. It's true though. The Xbox is only designed to suck air out of it through the exhaust fans. I have a simple analogy that shows this. Take a good look at the Xbox case, and imagine putting a little hole in the top of it, sticking in a plastic tube, and blowing in it. Then imagine where the air will go, - out all the ventilation holes and nowhere near the heatsinks. What would make it worse though is if the air went straight to the exhaust fans, bypassing the heatsinks.
Most people put the fan right above, or partially above the heatpipe extension on the GPU heatsink.