File servers are uninteresting things. This particular one does have a few interesting features though. I built it to be as quiet and cheap as possible, so I made it from spare parts of old computers (older stuff usually being lower power), the main parts being an Athlon XP (underclocked to 1GHz to save power) in an IWill XP333-R motherboard.
I used a compact flash card instead of a mechanical hard drive for the OS, since this both saves power and produces no noise, using a CF-to-IDE adapter so the server can boot straight from it. This is why there is an ugly yellow IDE cable visible in the interior photo running from the motherboard to the back of the case.
Everything else is stored on an ordinary mechanical hard drive, but to reduce its noise I suspended it on strips cut from old bicycle inner tubes. This is amazingly effective, totally damping all vibrations from the disc spinning, and almost completely absorbing all seek noise. Not being bolted directly to the case reduces cooling, so I positioned the drive adjacent to the vent in the front of the case to ensure it doesn't get too hot.
I use VNC to administer the system remotely, which unfortunately doesn't function unless a video card is present, so I installed an old S3 Trio, which is the lowest power card I could find (only a couple of watts). Cards like this are otherwise completely useless, so they are easy to find for free.
With the hard drive all but eliminated as a source of noise, only fans remain to silence. Due to the position of the PSU right over the CPU, it was possible to remove the CPU fan entirely, relying on the PSU fan to cool the CPU. I also removed the fan on the northbridge and fitted a larger passive heatsink in its place. This leaves the PSU fan as the only fan in the system. I connected it to one of the motherboard headers so it can be controlled by SpeedFan. It provides effective cooling, keeping the CPU under the set temperature of 40C (reported by a thermistor underneath the CPU) without the fan speed needing to be increased above the minimum possible 35% most of the time (I don't know what RPM that is because SpeedFan can't read it on this motherboard), with a slightly increased but still effectively inaudible speed necessary in the summer.
The result of this is a machine that cannot be heard at all under normal conditions. It also draws a relatively low 58W AC when idle (which is almost always).