Drifting pointer

Recently I was working on my father's work laptop cleaning off alot of spyware, replacing his anti-virus, and basically just cleaning up alot of mess (he had 77 running processes).

When I was finished I noticed that maybe every other minute the pointer would drift into the upper-right corner of the screen by itself. This is bothering me greatly because now nobody trusts me with  their computer now. I never do anything I haven't already tried on my computer.

Any ideas?

I've seen this on laptops where there's a fault with the trackpad. If you deactivate the trackpad (can often be done via that grey square icon in the notification area, some laptops have a button or switch to do it, and some deactivate it automatically when a mouse is plugged in) and pointer stops drifting, that's your problem narrowed down right there. In some cases this can be fixed by opening the case and reseating the ribbon cable from the trackpad unit to where it connects to the motherboard. But if there's a fault in the trackpad itself, it will have to be replaced.