Getting started

This may seem silly and obvious, but you need to start by listening to your computer and decide which noises are louder and more annoying. Is it the whining noise of hard drives? The hissing sound of air moving through high-powered fans? The humming of old and unbalanced fans? The klickety-clack of old hard drives? I recommend opening up your computer and disconnect fans and hard drives one at a time and listen to what is causing the most noise. With a little training you will be able to separate the noises from each other, which will help a lot when appreciating how much difference these procedures makes.

From my experience, replacing the fans in your computer with new fans is the single most effective way to reduce the noise it generates, but it takes much more than that to make your computer inaudible.