Random reboots are a pain in the ass! These are almost always caused by Windows STOP errors. STOP errors are hard to solve and its even harder to find the source of a problem. But this post is well worth a read as it describes step by step, the actions you need to follow to get rid of an stop error.
Read: http://filenetworks.blogspot.com/2007/03/how-to-diagnose-random-reboots.html
Read: http://filenetworks.blogspot.com/2007/03/how-to-diagnose-random-reboots.html
