Here there are some pics of my carputer; that's an Athlon 1400MHz ATX mounted on an Opel Corsa (Vauxhall). More specs:
case: wood & aluminium, handmade;
alimentation: 600W Inverter + 350W Pc ATX power supply, using a delay circuit to prevent inverter kill due to pc cue corrent;
alimentation: updated to an Opus 150W DC-DC, big efficency gain;
On the Motherboard:
Athlon 1400MHz, down clocked to 1050 MHz for thermal security; 256 MB Ram
Devices: 3,5" HD 80 GB Maxtor IDE, 5" Optical drive combo (DVD reader, CD burner)
Cards: Sound Blaster PC 128 (ess1370), Matrox MGA
G200 (prodly supported by DirectFB), Ethernet rtl8139
Input: ps/2 cable going under the passenger seat, usb2wireless remote control (it emulates a mouse)
Os: Slackware Linux 10.2 with tons of kernel/rc.d patches to reduce boot time
Many thanks for getting this crazy idea real to Daniel (the one on the photos) and Dario.