"It was over a year ago that I looked at Matrox’s TripleHead2Go – a
fantastic little device that enabled you to run three screens off a
single graphics output, with a maximum resolution of 3,840 x 1,024. Plug
it into a notebook and you could have those three screens in addition to
the notebook’s own - a four screen display, enough for even the most
desktop real-estate hungry user. What's it simply does it to present
itself to Windows as a single very large display, which you can then
divide up using the supplied software.