Welcome to mp3car!
Your best bet is probably to go with an aftermarket ECU such as megasquirt, and then use the PC to control it. Using a carpc, especially one with windows for a mission critical operation such as running the engine is an incredibly bad idea 9if even possible), and a really good way to end up stranded on the side of the road. That being said, using the carpc to control the aftermarket ecu is perfectly reasonable and there are some people who do it that way. What kind of car do you have?