Can't disable touchpad

I've been trying to disable the touchpad on my Latitude E6400 because of erratic cursor movement. The device manager doesn't show a mouse or touchpad icon. I selected my computer, scrolled to the touchpad and opened properties. The disable tab is not active.  Dell's site states:

Depending on the manufacture and software version of the drivers and software for your touchpad, an option to disable or enable the touchpad may or may not be available.

Does anyone know how to tell if my laptop is one that doesn't have the option to disable?