I don't think they are going to RCA, perhaps RGB or component? I say this because S-video does not carry sound, so a S-vid to RCA would only have a yellow, not 3
If your graphics card does not have the correct drivers (eg windows ones rather than the ATi or nVidia ones) It may not operate corrently, also, if the graphics card does not support TV-out it will not work.
What is the brand and model of your card?