Making S-video work with TV monitor

Has anyone had success with using a TV as a monitor for their PC? I'm trying to connect my son's desktop system with ATI Radeon AGP card to two TVs...Samsung and Sony. A B/W image appears but does not stop rolling. Have also tried using an S-Video cable as well as the RCA S-video adapter. Same result in all cases.

Are there any videocard settings which need to be made? What about the absence of a color image?

Any assistance or leads on resolving this dilemma is greatly appreciated.

Thank you.