S-video output

I want to use the S-video output jack to display documents which are open on my desktop to a TV or a video projector.  I can get the wallpaper to project by enabling the secondary monitor through the S-video jack, but when I open a document, the video out remains as the wallpaper.  If I function F8, it disables the secondary monitor and the external display goes black.  Of course I have tried function F8 toggles several times, but nothing.  I have also searched the Knowledge Base without any luck.  Where can I get instructions or limitations for using the S-video out?