While searching for a suitable computer for a home internet server, i stumbled accross this thing, and instantly thought CARPC!!!!!!!
I dont know much about it. and they dont use harddrives . But they are small, cheap and look cool. You could add a external usb harddrive though i suppose. It is 10.8x8.5x1.5. Onboard PSU, probably 12V with an external power brick
More info on it can be found here