I have this very setup on my work pc using a DVI splitter cable and a single output ati 1300 card. The computer runs windows 2000 and on the left screen (screen 1) I can have normal operation and on the right screen (screen 2) I can display what I want.

You will still set your screen to; extend my windows desktop onto screen two, but it "does" not combine the two screens into displaying 1 massive image. Each screen works independant of the other.

If I open a window on screen 1 and click the fit to screen option it will fit to screen 1, I then open another window anddrag it onto the second screen and click fit to screen and it fills screen 2.

I this is what you want to do then I would recommend a PCI express ati 2600 if you want HD playback.