how to disable the device on a laptop?

what are you getting that makes you think it is malfuntioning? whether you get 4 or else of u, 5 instead of i, 6 instead of o then you human the Num Lock active, press Fn and the Num Lock key and it should fine.
If you are exploit double letters once pressing a single key later it is record likely damaged. Peak laptops don't allow you to disable the keyboard though some do have an option in the BIOS, check it to be assured.
To disable the on-board keyboard you will involve to detach the data ribbon, leave the keyboard in place as this will keep down the dust and other debris and keep it more electrically safe.
You shall need to procure the upright off, this is not too difficult and the best option is to check for screws at the bottom of the laptop that will grasp the Kb in place, the highest I believe has spring clips that you just fling to release with a small flat headed screw driver. Unclip the cable, tuck it out of the way and replace the keyboard and use a USB alternative or buy a new advent keyboard.