||MS FS and X-plane support multiple monitors. A dual head
video card like Nvidia Ti 4200 can be used.
You can use the second monitor to widen the view: After installing the NVidia drivers, a utility will allow you to select desktop span. The desktop will now be stretched over both monitors. In X-plane or MS-FS, you can then select 2048x768 resolution, and have the scenery and cockpit view spanned over two screens. In MS FS, the cockpit view van be undocked and resized.
The biggest drawback of this setup is that you always have a transition in the center of the screen. This is quite irritating at landings. Also the cockpit is split in two halves.
Another option with dual screen video cards is to split the screens into one scenery and one cockpit view. This is a nice method, as you create a real separate outside view, and can build the cockpit view into the housing of a simpit construction. A 17" or 18" LCD panel is big enough to show most instruments and extra instrument views like radio stack and GPS.