1. A machine-implemented method, comprising: on a portion of a primary display device of a computer system, the computer system generating a display; if the computer system is in a first mode, then on each secondary display device in a set of one or more secondary display devices of the computer system, the computer system generating, within a portion of the secondary device, the same display that is concurrently being displayed within said portion of the primary display device; if the computer system is in a second mode, then within the portion of each secondary display device in the set of one or more secondary display devices, the computer system generating a different display than the display that is concurrently being displayed within said portion of the primary display device, wherein, when the computer system is in said second mode, the display generated on the primary display device displays controls for selecting what is to be shown on the portion of said one or more secondary display devices; and switching between the first mode and the second mode in response to user input.