Abstract: A pen-based portable computer, or pen-tablet computer, for use with a vehicular docking station that allows for the exchange or replacement of components thereof without the need for returning the computer to the manufacturer. The computer utilizes a main or primary housing for the major components of the computer, and a separate, independent, auxiliary expansion unit having its own housing for mounting a replaceable radio module that is connected to the main computer via a multi-pin connector, whereby the replacement or exchange of the radio module for a different one is easily and readily achieved, and where auxiliary or expansion devices may be connected to the main computer thereby, and where the auxiliary device itself serves as a handle for holding the main computer.