Cannot disable touchpad on my HP 450 G6

Hello! I see you've already written about this issue, however the solution proposed doesn't work for me. There's no light on or near my touchpad, and no obvious switch. There's no on/off toggle in the mouse or touchpad areas of settings. Double-tapping the upper-left hand corner of touchpad to disable it is not doing anything. Updating the driver didn't change anything. This is a brand new machine and the over-sensitive touchpad is driving me insane and keeps sending my cursor all over the place! In case it's relevant, I have my external mouse plugged in. Please help!