possible to disable touchpad with external mouse?

[Anchundan]

Is it possible to get my laptop to disable the touchpad whenever it realises there's an external USB mouse connected?

I find it really irritating to be typing then suddenly find the cursor's jumped position because I accidentally pressed the touchpad.

I know I can disable it permanently in device manager, but that's no good when I don't have a USB mouse handy (i.e. very difficult to re-enable it without a mouse).

I have an HP/Compaq 6720s, running Windows XP.

 

[Anchundan]

I've been looking for that, unfortunately, it appears to not be synaptics. Device manager says it's a 'PS/2 compatible mouse' manufactured by logitech. There doesn't appear to be any option under mouse in control panel.