has anyone tried this?
I have a mobile athlonxp in my desktop. I usually run it overclocked at around 2.8GHz, but I was able to run it at 1.0volts at 1.5ghz. VERY LOW power consumption. If you are going for a desktop system in the car, I would recommend using a socketA motherboard with mobile athlon support.
A slightly underclocked one of these: http://www.newegg.com/app/ViewProduc...103-440&depa=0
should be able to run at 1.1v, using around 15 watts.