I just got out of a fascinating session at WinHEC on designs for new Media Center PCs. Nvidia has been researching heat and noise in PC design, with a special emphasis on creating PCs that are quiet and cool enough to pass the living-room test.
Heat comes from some surprising sources. If you select the right CPU, it will probably pass the heat test with flying colors. Under heavy loads (recording two programs at once and playing back a DVD), the most heat came from graphics processors, tuner cards, and hard drives, all of which easily hit 60 degrees Celsius (140F).
The challenge for the next generation of Media Center PCs is to cool down all these components and keep fan noise to a minimum and put it all in a case that fits in your audio rack. That’s a tall order.
Some great links on the final slide:
Case and fan designs:
Quiet PC specialists:
I have yet to find aPC quiet enough for my living room, which is why my Media Center PC is in the office and a Media Center Extender is connected to the TV. Custom home builders have been hiding audio/video equipment in closets for years; maybe this technique is ready to move into more modest homes.
Ed Bott 
I recently upgraded and paid a premium for a quiet pc case …
Well the case fan was very large and quiet enough….so was the power supply fan.
However all this quietness just made audio room for the very noisy cpu fan trying to cool down a P 3.2g.
How about incorporating sound cancelling technology into the case?
This works well in the headphones for pilots trying to quiet down very noisy areo engines.
I suppose it is possible but cost would be a factor …however a cost I would gladly pay!!
I hate noise …..!
jp