I've done my own one before, you will need for a double DIN, single is too little space for most ITX, but a PicoITX board would fit, if you had the money.

I don't know if I've got any old pics :( I'm Skybarge over on Mp3car.com and a few other sites

- PSU round $120NZD I did mine 2 years ago using an M2ATX but i don't recommend it, get a 250w or M4ATX. Make sure it has variable range voltage from about 8-18v, just so it survives engine cranks. Also see if it can be set using jumpers or firmware. I had mine for power on after 15 seconds, power off 30 seconds after ign off, forces a shutdown command.
- Mobo round $157 if you wanted dual core d945gclf2 atom
- $40 2GB DDR2 ram
- CF to SATA converter, get the fastest you can afford $30 from ebay
- CF card at least 4gb if not larger, make sure it's not a fake and get a fast one
- 2.5" HDD if you wanted or just use a removeable for music etc
- Double DIN holder to suit car, I used a infiniti maxima dash, even though mine was a skyline
- perspex - from bunnings :)
- 7" TFT Touchscreen - perfect size for a double DIN

$747+ depending on exchange rate and prices
Basically make a box out of perspex and remove the old screen braces/cover and mount it into the new Dual din holder/faceplate.
make sure it fits in the car

- Mount the mobo at the bottom of the enclosure, cut the holes for the input/outputs for the mobo
- Hardwire the touchscreen onto the USB header, I just used an old case USB header
- Mount the HDD at the top of the case to the right or left and mount the PSU next to it, if you are including it
- The Sata/CF adapter can be mounted on the 2.5" HDD


Basically get it how you want it too look after that, it's a lot of fiddling, but worth it :)

Use a copy of WinXP nLited or Linux MCE. MCE is a bit experimental and might need some work done. WinXP is easy and you can load up any front end you want. I tested mine with FrontRunner, good system. There's also frodo player(but it's been abandoned last time i was there) but you can get the visual Basic code and crank some stuff up