My laptop PC is a HP G5055EA and I tried some scripts and applications to disable its touchpad, but no one works permanently: some of this software disables touchpad only for a few minutes and others does nothing at all!
Your laptop should have a key combination to disable the touchpad still if you are asking for a software then you can search in the software centre for pointing devices and install that.
you'll find it in system > preferences > pointing devices
there you'll find the option to disable touchpad under General tab
Many laptops have a hotkey (Fn + Touchpad key) which should Switch On/Off a touchpad under Ubuntu as well (like it works in Windows systems). However, such keys combination doesn't work in my Asus K52F (which has a new i3 Intel chipset).
I found that Jupiter applet link text works very well in my case.