Uninstalling drivers won't work because windows will acquire it automatically. Also you can't disable it through system device manager.
So there are two ways.
1. Unplug the connector inside the laptop (but that would be more effort than cleaning the keyboard)
2. Disable your device using DevManView
2.1 Download DevManView
2.2 Sort list by "Device Type Code" and search for "Keyboard"
2.3 Internal keyboard will be called something like "PC/AT Enhanced PS/2 Keyboard (101/102-Key)"
Right-click on it and you will be able to disable it
(You might get an error -xxxxxx, but that does not change anything)
2.4 Restart your computer and Voila!
You will be able to enable it anytime by using DevManView or system Device manager, and restarting the computer.
EDIT: This might also disable your touchpad. So you might need a USB mouse too.