As payback, his coworker changed the keys on his hp keyboard to read knob head!.
an HP keyboard with the buttons changed to KNOB head at the top
An hp brand keyboard has had the keys rearranged to say "knob head" across the top row.
HP Keyboard that says Knob Head, and has the text on top saying: You mess with my desk, I mess with yours...
someone changed the keys on the top of a keyboard to say knob head