An assembly for attachment to a portable computer is described including a touchpad and associated buttons where the touchpad is mounted on one surface of the assembly and the associated “mouse” buttons are mounted on the reverse surface, the two surfaces facing in substantially opposite directions. The buttons are mounted in close proximity to the reverse-mounted touchpad such that the user can operate both the touchpad and the buttons simultaneously with the thumb and one or more fingers of the same hand. In one embodiment, the touchpad faces away from the user and is operated by a finger that is not the user's thumb. In another embodiment, the touchpad faces the user and is operated by the user's thumb. For all embodiments, the associated “mouse buttons” are mounted facing in the reverse direction relative to the touchpad.