I recently ran into this problem on my Dell Latitude D820. The problem
appeared after I had been using Vista for several months so I'm not sure
what caused it. However, the symtom as described above, was that when I
placed focus on a window the cursor would jump around making all kinds
of selections in VS2008, screwing up my Word documents, randomly doing
things to my mail system, and making all kinds of selections in my
browser. At first I thought I had a virus. After searching for my
symptoms I ran into this thread and the discussion on the touchpad clued
me into what was happening.

The fix was to download the latest touchpad driver from Dell, install,
and reboot.

I recommend disabling your touchpad and running with a USB mouse
(obviosuly if you are traveling this won't be practical). If for some
reason you don't have a touchpad showing up in your system tray then
this is another indication that your system is not properly set up.


--
nixonmark3