I just got through building out my ITX PC - it measures 5.7" x 6.7" X 1.2" with the power supply plugged in. I'm using a 2.5" 20 GB hard drive and a slim DVD-ROM. The DC to DC converter (power supply) has the proper power connectors for both units. Instead of using a store-bought case, I'm going to build the computer into the custom overhead console I've just designed and installed, with a GPS receiver and audio out to the in-dash stereo for MP3s and DVD sound. My last to-buy item is the display. I'm getting a Xenarc 7" (800 x 480) VGA monitor which will be mounted to the outside of the OH console center module. I have the whole shebang on AutoCAD, if anybody is interested in doing something similar.

The PC was a piece of cake to build and even tho 800MHz is not fast compared to regular home PCs, it is plenty for an in-car application. Also, if anybody has any info on other types of software that might be useful on a car PC I'd be interested in hearing about it.