If all is working, so far, with the mouse, I'd use some compressed air to blow out the rest of the stuff you saw in there. Dust/dirt can slow the performance.

For repair, go to the Start menu (it displays with the Windows icon - bottom, right side of the monitor). Opt for Help and Support and input the key term Repair.

I'm using my Vista right now, and can't recall if XP's option to repair is under Add/Remove Programs (in the Control Panel).