This is a very hacked together Pentium 3 system with only one fan.
Pentium 3 550MHz passive cooled
Supermicro P6SBU motherboard
Geforce FX5600 + Accelero S2 and ramsinks
Seagate Barracuda IV 60Gb
Soundblaster 128 PCI
SiS 10/100 network card
Evesham Micros case circa 2000
It contains parts from about 10 different computers over the last 15 years or so and hardly anything can be considered standard.
The CPU came from a broken old medical system. The standard heatsink and fan was loud, initially I replaced the fan with a slow 92mm but then recently I replaced the whole heatsink assembly with than from a broken Athlon 700 system. This allows it to run without a fan and hasn't broken 48C yet.
The motherboard was from the same broken medical system. It has a serial port missing as this was desoldered for use on another motherboard. The board has an onboard SCSI controller which is disabled. Clocking and voltage options with this motherboard are not great.
The RAM comprises a 64Mb and 3 128Mb sticks. The 64Mb came with the motherboard and CPU from that broken medical system while one 128Mb stick came from a colleague who was throwing it out, another 128Mb came as stock from that Athlon 700 and the other was an upgrade for the Athlon 700. All running at PC100.
The graphics card has had a BIOS mod to lower 2D volatge and clockspeed. It's previously been in a Shuttle, another Athlon XP system and the broken Athlon 700 system with any number of coolers on it. Now it's got an Accelero S2 which doesn't quite cover the whole chip so isn't ideal and a set of ramsinks from both an Iceberq 4 and an Iceberq 4 Pro. Temps tend to range from the mid fifties up to the low seventies. I also have a passive Radeon 9000 Pro at my disposal which could be used as an alternative.
The hard disk is one of the quietest I know and is currently mounted in a plastic caddy in a 5.25" drive, this could be improved. This drive has been in three different systems before.
The optical drive originally was fitted to a Shuttle although has also been in the broken Athlon 700. It makes a nasty noise on startup when it searches for a disk. I have an LG DVD drive which could be used instead if CD writing isn't a requirement. The floppy drive just came with the case, not too exciting and totally unmodded.
The Soundblaster 128 was one of the last 2 channel Soundblasters. I also have a CMedia 5.1 channel card available but it doesn't work so well with a lot of older games, hence the Soundblaster being used instead. This card originally came with the broken Athlon 700.
The SiS network card is one of a few I have available. I may swap this for another based upon compatibility if one works better under older versions of Windows.
The 230W PSU is an early ATX one from a P166MMX system made in Jan 1997. It originally had a 92mm Mishina fan on the underside of it blowing downwards through the case, this was the early ATX cooling layout. The fan was temperature controlled and up until a few years ago was the quietest I'd ever used, mostly because so many 80mm fan models are so bad. In that position the fan would foul on the Slot 1 CPU so I first put the fan inside the PSU blowing through it. This worked fine. What I have now done is replaced the fan with a Silverstone FN91, powered off the same thermally controlled header. This is a lot quieter. My attempt at RPM sensing hasn't worked but I expect it spins around 1200rpm. This is the only fan in the system.
A close up of the PSU/CPU area with the systems only fan:
The case was originally used for an Athlon 700 system where the motherboard blew. It has a pair of 80mm mounts, one at the rear and one at the front and a few fent holes elsewhere. Both of the 80mm mounts could be remodelled to be 92mm or perhaps even 120mm mounts. Annoyingly it came with a little shelf that stuck out under the PSU which I had to cut off with tinsnips. The edge can be seen in the above photo.
The system is set up with a Compaq S710 monitor which was being thrown out at my mother's office, an Advent keyboard which I got with a FREE AST P90 system in 2002 (and I'm sure that wasn't it's original keyboard), a Logitech wheel mouse and a set of Cambridge Soundworks 2 channel speakers.
It currently has Windows 98SE (although this is broken) and Vector Linux 5.9 on it and is used for emails, a bit of browsing and old games... when Windows is fixed.
Sound wise it's almost the quietest computer I've ever used. The Hard disk could be remounted better as the seek noise is still audible and the PSU fan could be replaced with a 120mm unit with a bit of cutting. Some sound deadening work on the case would also help.