Here's my Pentium-M based PC that I've got stashed away under my TV. Items of interest are the PicoPSU and the motherboard.
The motherboard is Intel's 915GM evaluation board
, left over from some work I did last year. Processor is a Pentium M 760 (2GHz). The motherboard has no onboard audio so I use a Turtle Beach USB adapter to provide a SPDIF output. TV output is courtesy of the 915GM chipset.
The evaluation board game with a pretty basic heatsink with a screaming 60mm fan on top, that had to go. I ended up keeping the heatsink since I couldn't find a way to mount anything else and then suspended a 92mm Zalman fan over it using a Zalman bracket. I think it's a pretty good solution. I've used a Nexus fan controller to keep the speed way down, there's no RPM sensor on the board so I don't know an exact speed. I've kept the 120mm Coolermaster exhaust fan that came with the case, again with the speed kept way down - I think I could probably do away with the case fan entirely to be honest.
Hard drive is a Fujitsu laptop drive that I mounted using some foam and a zip tie.
In terms of silence, I can't hear it at all unless I'm a foot away. From the sofa the only way I can tell it's on is from the ugly blue LEDs on the Nexus fan controller. The Motorola cable box makes way more noise