I have a mid-2007 MacBook Pro, the one with the trackpad that had the physical button on along the bottom edge. The trackpad is not well and using it can cause it to stick and freak out OS X.
Is there a way to disable the trackpad that's a little more low-level than the method outlined in this question and answer? A BIOS setting perhaps? I'd like the trackpad to never be useable on the unit, whether an external mouse is connected to it or not.
Best Answer
You should be able to do this by unloading the kernel extension (kext) that controls the trackpad from the command line.
sudo kextunload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTrackpad.kextto disable it. Changekextunloadtokextloadto re-enable it.When I tested this, it complained that it couldn't unload the kext, but it appeared to disable the trackpad (and it didn't show in System Prefs) despite the warnings.
Warning for Magic Trackpad Users: I don't have a Magic Trackpad, so I don't know whether this kext is responsible for that device or not. Careful testing this out, you may accidentally disable all your mouse inputs at once.
Edit: I did a little more digging, and there is a "AppleBluetoothMultitouch.kext", which sounds like it's responsible for the Magic Trackpad, so it's likely you can disable the internal trackpad independent of any external ones.