aaah man, there was a time i was obsessed with this idea but i realized that its just too costly and unstable.
Fitting a hard drive in your car is not a good idea. Using Windows XP will be a great headache as u'll be rebooting every now and then. It will drive you crazy! You will be making alot of direct shutdowns even the most intelligent power supplies won't handle the cranks which will often corrupt the file system on your HD.
A weak car battery or a self motor consuming liil extra amps will cut the power to ur CPU.
Its better just to fit in an IPAD. It will cost you like 40-50 ks. Its much faster has inbuilt GPS etc and has less moving parts.
If you still want to take on the project, i would you keep the costs to the minimum. You are trying to invest way too much in the hardware. You should just get a thin client from EBAY it should cost you around 50 USD. thin clients are quite capable with usb ports so you can hook up your devices thru that. For power i'd suggest installing a UPS. It will prevent abrupt shutdowns and give you chance to switch off everything by ur self thru a remote.
UPS set up should cost you around 5-8ks (Dry battery type , small ones)
External shock proof hard drive 320 GB should cost you around 5 ks.
Extend USB & VGA Cables to the front and keep rest of the equipment in the boot. Use a USB HUB at the front.
Try to use a light and stable os, may be ubunto ? or the entertainment platforms being used in netbooks keeping ur boot time to the minimum.
For internet, just get a wi tribe or world call usb dongle for 2k they offer decent speeds
Thin clients mostly have inbuilt wifi adapters.
Get an infra red remote kit, comes cheap.
blue tooth dongle is available in the market for 2oo rupees
Without screen the setup should cost you around 18K (with back up power) .
You can replace the HD with SSD and you will have better speed and stability but SSDS are expensive. You can get one later if everything works perfectly.
Good luck!
