An excellent solution is a new breed of power supply that can make decisions about how to supply power and even signal a PC to 'hibernate' or 'shut-down' when warranted. It's called a DC-to-DC converter, and it can covert a car's 12-volt source into the 3.3-volt, 5-volt, and 1-volt outputs that computers can use. I especially like the M2-ATX. It allows for a user-selectable timer that lets the PC to remain on for a certain amount of time after the car is shut off before issuing a command to the computer to go to 'sleep.' Then, after a prolonged period of sleep, the power supply protects the car's battery by issuing a full shutdown command to the PC.
Vibration and shock: Components in a car PC are subject to all the same jarring, bumping and G-forces as passengers are. If all users drove luxury cars on traffic-free, freshly paved highways, then vibration and shock would be a non-issue. But in the real world, potholes, debris, curbs, and sudden stops and starts can all cause serious trouble for an in-car PC. As a result, hardware mounting, cable stress and wear, and choice of hard disk need to address the situation.
The PC's hard disk is the only constantly moving part, making it the one most sensitive to road shock and vibration. Fortunately, most of today's 2.5-inch notebook drives are designed to take a reasonable amount of abuse from motion, and most are suitable for all but the most rugged applications. I recommend the Seagate Momentus 7200.1, which has been rigorously tested for use in many mobile and notebook applications. For situations where you know your car PC will be heavily stressed, Seagate's EE-25 series drives are hardened specifically for automotive applications; they should hold up better in challenging applications.
Operability: Car PC users need to get to their applications fast and with a minimum of interaction. So keyboards and mice, while handy for occasional work in the car, are of limited use in a car. Instead, car PCs should rely on touch screens and software interfaces with "skins" that let users access their apps quickly and safely.
In car lingo, a touch screen works like a "head unit," providing access to music selection or a GPS. A major goal of a car PC is to replace the vehicle's head unit with a touch screen that will act as GPS, CD player, radio and the like.