XP Home on a laptop has buttons jumping

Any and all buttons, OK and Cancel among others, will do a weird rapid switching like something is clicking them really fast. It even happens in Safe Mode. Other weird things like windows opening and shutting, or not wanting to shut are happening also. I scanned with AdAware SE, Spybot 1.3, Norton Antivirus 2003 and an online antivirus scanner. Nothing is showing up. They also purchased a new mouse but that didn’t stop it. It’s driving the end-users crazy. Help!