Question about dual displays via video card

I have the P4R800-V Asus motherboard that has a built-in ATI RADEON 9100 IGP video card. I want to be able to display normally using the VGA port to the computer monitor, but at the same time display that same desktop to a secondary monitor (a 32 inch television) using the S-Video output. In going through the setup, the best I can do is "Switch back and forth" between the displays and not have both up at the same time. It will not let me "extend the desktop to this display" in the display properties. Is this because of the use of the built-in video card or is there something I am missing? Perhaps a free driver download somewhere that would fix this? Any suggestions would be great. I just want the display to be on both the monitor and the TV at the same time all the time.

Thanks.