Computer noise can have an adverse affect on recording and music-making in a studio. I ran across this article that you may find informative and helpful. Big Bruin/Geeks.com sponsored some Tech Tips on reducing noise in PCs in their article: "5 Simple Steps to a Quieter PC".
Although there are costly solutions, this collection of tips offers advice on reducing the noise from your PC on a minimal budget. The author suggests "Before starting on any sound reduction upgrades, analyzing a system to pinpoint the areas in need of the most attention will help determine the best course of action and the best way to spend any money." The author discusses reducing noise in Cooling Fans, Cases, Fan Controllers, Power supplies, and Noise / Vibration Isolators.
If anyone has tany thoughts, ideas or suggestion on reducing computer noise, please list them on this thread. Also, if you know of any products to combat noise please let us know. Perhaps we can gather many of these tips and make a tutorial.