Well I currently don't have the cash, but I was thinkin any other mamers with the extra dough and the wiring skills might find this interesting. So I was thinkin to myself, how could I cheaply put a PC into a car? Cause all those screens I was looking at were like 600-700 bucks a piece. Ebay of course.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3031538189&category=14946 -$199 for a monitor that hides itself into the dash when not in use, and looks like a radio, and comes out full screen.
http://www.pricewatch.com for a cheap computer with an ATI video card, you'd probably only need up to like a 1ghz processor, because the most you're going to be doing is playing movies.
http://www.ultimarc.com for an Ipac to make your own control panel on the front using either radioshack buttons or even possibly arcade buttons. You could also try to integrate a trackball for the mouse, that might be kinda interesting.
You'd also have to buy a wiring harness which is only like 15 bucks, and some type of shock absorber, such as those aerospace foam pillow things for the hard drive so it wouldn't accidently delete some data when going over a pothole or something. You would probably also want to mount the whole thing on something like a wood block, maybe a triangle or something like that to prevent dust from getting into the processor fan, etc. You'd also have to buy the cables to connect the computer to the lcd screen if the one they include is super short, and also probably some other stuff I missed.