Build a Quiet Computer
Extreme Tech has written a very good article about building a computer with a very low noise output. They write about the main things you should think about when you build your computer, which components you should use and so on.
Read the whole article [url=http://www.extremetech.com/article2/0,1697,1902996,00.asp:1hyipl95]here[/url:1hyipl95].