When I see this issue I boot from my Linux LiveCD (Ubuntu from google.com) and see if it works or not. This helps me figure out if it's the os or the machine.
I have Vista Ultimate on a Dell XPS M1330. I cannot get any USB plug in mice to work on this system. I've uninstalled the drivers and reinstalled them. I've done a system motherboard test check to no avail. Now I've been informed I should reinstall Vista....however, before I do that, I'd like to know if others have had similar problems and the resolution.