I haven't read all the replies but any time you acoustically treat a computer you increase the overall temperature so there's definately a trade-off involved. If noise is a problem then the best solution would be to simply move the computer far enough away from the mic so it isn't picking it up. Extention cords for keyboard/mouse/monitor are cheap. You could also try quieter fans but whenever air is moving it's going to create noise so that may or may not work for you. And finally, the more harddrives you have, the more noise there will be period.