The S3 video cards (for desktop) and built in (part of motherboard) do not support any type of dual display. The S-video plug you have is so you can switch to a TV to display DVD movies or play games with the larger screen, but you can not split the video. Also, there is no way to replace the video on the laptop as it is always a part of the motherboard circuitry. Sorry to burst your bubble but what you are wanting is impossible.
Your only option to get dual display is use a desktop computer with an ATI Radeon card or get a different laptop with the ATI Radeon built in.