I have a Dell Inspiron 5040, and I cannot disable the touchpad.
The best solution would be if Ubuntu could actually not ignore the keyboard shortcut that disables it.
Nothing did the trick for me, so I made the following little script that works:
Well i am not sure if this program could help you but there are a some options to disable the touchpad.
The first option is installing Jupiter, this program is pretty usefull and has other funtions like change the performance modes and obviously disable the touchapad, to install it:
Other option is install an applet that disable the touchpad, this is an applet that disable the touchpad: