A hand-held portable computer is provided with a control wheel to accelerate navigation and selection that is otherwise difficult due to the small form factor of the portable computer. The wheel is turned in a first or in a second direction to scroll through an on-screen menu. The wheel is pressed to select a particular item from the on-screen menu for execution. Context-sensitivity is provided in that the underlying software determines which menu to display or command to execute, in response to dialing or clicking the wheel, based on which application and pane are currently active and based on which item in the pane is currently selected. User-configurability and extensibility to additional applications are provided, without modification of the underlying software application code.