It *is* actually possible to build a totally silent PC. I built one myself: No fans, the only moving part is the HD (Samsung 1614C), which is mounted into a special enclosure to further reduce the noise. Just to give you an idea *how* silent it really is: I think about getting an TFT display because I find the sound that my CRT monitor makes annoying...
The only internet resources I know are in German language. But you might have a look at
www.deltatronic.de (page available in english). They are quite expensive, but it is definitely not necessary to spend so much money if you don't need high end performance, just a quiet PC for work.
My setup is: DFI infinity NFII mainboard, AMD Barton 1,8GHz mobile processor ==> *under*clocked to 1,6 Ghz, core voltage reduced to 1,25V, low-end passively cooled graphics, Samsung HD, fanless power supply, "Mercury Aero One" case. Whole PC costed about 700 Euros.
- Using a mobile processor in a desktop PC is a little bit more expensive, but they produce less heat. AMD is better than Intel at the moment. Look for mobile CPUs with "Barton" core.
- In my case reduction of core voltage to 1,25V and clock speed to 1,6 GHz decreased power consumption of the processor to 25 W max (!!!), it can easliy be cooled without a CPU fan.
The system is "always-on" and has been up and running for several month now. It is totally stable even under full load, processor temp never rises above 50°C.
Or you can get an Apple PowerBook. I have one as my main machine. The fan is *never* running on the current models, so the only thing that makes noise is the HD again. Get a silent one (4200 rpm, not Toshiba) and it is really very quiet too. And it has bit-perfect digital out, too
Now I may have been completely off-topic, but I figured some of the above might be interesting for you...
Andreas