There was a problem with the first trackball that was shipped with the Aero's.
This occured on all models of the Aero. New units are now shipping with the new
trackball.

The problem was one of being too slick. The ball was polished and shiny. Any
oil, dirt, fluff, etc. that would get under the trackball would cause it to not
work properly. Compaq came out with a "roughed up" version that fixes the
problem. Call Compaq at 1 (800) 841-2761. I believe that this is the only 800
number to call. If you are outside the US, call your local distributor, or call
Compaq directly. They will send you, free, a trackball cleaning kit and a
high-friction replacement trackball. All you have to supply is a serial number
and a shipping address.

or you can sand it down:

From:(Beloved Recordings)
I don't recall whose brilliant idea it was to sand down his track ball to
create a less sensitive device, but I would like to thank him.  I tried it
out with some sand paper I have in the house and I have not had any
problems with the ball yet.