On my little transmeta crusoe "server" my 40 gig hard disk was wearing out and making enough noise to give me a head-ache. So I replaced it with a 30 gig laptop hard disk. There's a very faint high pitched noise that requires some work to hear.
I suspect if I could find a box to put the computer in I should be able to muffle that noise. The only other moving part is the power supply (since the crusoe is efficient enough that it doesn't need a CPU fan). Since the entire computer is only using about 20 watts, I could actually use a fanless power supply.
Though I'm not sure if I should go for a fanless AC power supply, or if I should get the battery, charge controller, and a DC power supply that would be the first steps toward solar powering my computer.
The other part of going for a quiet home compute environment is that I've managed to get diskless workstations to boot as well. Although the 486 didn't have enough oomph to be that useful, the only noise it was making was from the rather tiny CPU fan.
So it'd be nice if I could get a more modern system to be silent.
I recently discovered that at least one Pentium 4 model can be run fanless. (It slows itself down sufficently to prevent a meltdown.) So given a good heatsink it should perform reasonablly, and perhaps low enough power to go for another one of the fanless power supplies.
Which leads to the joy of a thin client with absolutely no moving parts.
Then with a file server in the closet, I could have a reasonable compute environment and silence.
Now if I could only optimize for power usage at the same time...
(Such odd goals I managed to develop.)