So work is progressing nicely on my car PC. I need a laptop hard drive, a power supply, a case, and some sort of interface, likely a 7" touchscreen. The case I can do myself, no sweat. The power supplies are making me pretty irritated, because they cost $80, AND it's really only a power conditioner anyway. It's already DC power, which computers (and most electronic devices) use anyway, so there's no transformer like in a tower PSU (which start at $15 ANYway). It's tempting me to make my own. So I'd need to base it on car electronics. I know that you want a nice large capacitor (I've heard mention of a 2 farad version, but I don't know if you really NEED that much) to prevent popping of an audio amp, and power surge during cranking of the engine. That should also help somewhat regulate the voltage at other times, and I'm thinking in general I could take the concept farther in conditioning the power to make sure I get a steady 12V flow, or at least prevent OVERvoltage. and the wiring should be a snap, too. I'll have a 12V DC input, and need to convert it to DC 12/5V. Anything else I need to know/do to make a standard ATX power supply work off a car battery?