Big wordy description first, then pics at the end.
A few months back I was in the local Goodwill, browsing for old electronics and interesting stuff. Came across a small "aluminum" briefcase, similar to the ones people used(and still use) to make a luggable gaming box. They're really just particle board with aluminum corners and a plastic "foil" over the particle board. Anyway, this one was $3 and had a plastic tray that looked like it was meant to hold playing cards or something similar.
Got it home, ripped out the plastic, started measuring, and found I could squeeze in a Mini-ITX motherboard, or one of the 3.5" Embedded boards I seem to have too many of. Did some more measurements and checked location of components, then decided on an Axiomtek SBC84810 embedded board. This one has an onboard Celeron-M ULV 1GHz and 1GB of DDR333, running at 266. Currently booting XP off of a 16GB Compact Flash card. 47MB/s read, 15MB/s writes. Nothing special, but it adds no extra components, uses little power, and honestly doesn't perform that badly.
It is also passively cooled, only a large heatsink, so I knew I would need some air movement to keep things from overheating. I also knew I wanted to use one of my spare roentgen gauges to show hard drive activity. Got out the hole saws, measured off, and put in one for a fan and one to mount the gauge. Grab a spare 80mm Panaflo and an atomic fan grill, and I was off. Get out the smallest hole saw, drill another hole, then install a cheap vandal power switch.
Then started the real work. Because the areas where I intended to mount the board and ports were made of particle board, I knew there would be no way to cut everything and have it look good. So I did the obvious. Since these are referred to as "Aluminum" briefaces, I drilled the rivets, removed the particle board, and cut and riveted back in a piece of actual aluminum. Used a solid piece on the side the board is mounted, and a piece of perforated mesh on the other. This way the air being blow over the board has somewhere to go. It actually flows quite well, and the fan is pretty quiet.
The board has serial, VGA, USB, 10/100 ethernet, and a PS/2 port onboard, but I left the PS/2 port hidden since I only have USB keyboards and mice. The vented side has the power input, audio line in/out /mic in, and two more USB ports.
For power, I'm using a Pico PSU mated to the power cable supplied by Axiomtek. They use ATX, but with a non-standard connector. If you'll look closely in the pic, you can see the cable just stuck into the PicoPSU. It's not permanent, since I'm going to throw in a different PicoPSU. The current one is a wide-input model, which this doesn't need. For now, it works.
I also need to rewire the gauge and add a power LED into it. The gauge is working, but I want my wiring cleaner and without any masking tape holding wires in place. Again, for now, it works.