Ultimate low noise PC: Samsung PC-over-IP Monitor
 

Video demo of a new Smart Monitor that uses PCoIP for remote desktop over standard IP networks - all 3D graphics, all applications, and all USB peripherals. Includes support for long distance WAN networks up to 10,000Km.

So put your PC in the basement, install a monitor/keyboard/webcam/memstick-reader/mouse on your desktop and you're good to go. While I've seen thin clients do Office applications at zero noise, this solutions offers support for 3D apps as well as HD video!