Has the computer been working indoors? I have had issues with just throwing in a old hard drive and it will do that looping reboot (or sometimes just blue screen). I have also had that happen when there was not enough power, might make sure you routed the recommended size wires and such, so the power supply has adequate power to work off of. Just a couple generic thoughts.
By the way, just noticed this thread....
http://www.mp3car.com/vbulletin/show...threadid=22865