Int 15 Fn C200  - System - Pointing Device BIOS Interface (ps) - Enable/d  [M]

   AX = C200h
   BH = new state
       00h disabled
       01h enabled

Return: CF set on error
   AH = status
       00h successful
       01h invalid function
       02h invalid input
       03h interface error
       04h need to resend
       05h no device handler installed