So it gets past the BIOS loading, and starts to load the operating system, right? Have you tried Safe Mode (pressing F8 while starting up)?
Software or hardware issue, that is the question... I would get a bootable Ubuntu live CD (doesn't need to be CD, can be put on USB too), and try to boot on that. If it works, there's a good chance the error is Windows related, and a backup - system recovery/reinstall would solve the problem.