Computer question - another compy suddenly loses mouse control

[Chojin]

So I just got a call from Emily's dad this morning, telling me that his mouse suddenly went to the left side of the screen and stopped moving. He tried replacing it with a PS/2 mouse and restarting, but still isn't getting any functionality out of the mouse.

My solution for this would be to try booting in safe mode, then try a repair through the XP install CD. But I'm interested in YOUR conjecture as to how or why this happened in the first place and any possible solutions you may have.