I may be stating the obvious but your TV is S-video compatible right? Otherwise if you get a signal out it'll be in B&W.
You need to enable the s-video out port. Switch TV on and set to the correct AV input. Right click on desktop/display properties/ settings/ advanced. Look in this section for settings. You may need to enable it as a second monitor for example.
It woud help to know what graphic card you have.
Also look at the functions of your laptop. There might be a special function to enable the board eg: on mine FN + F3 is supposed to activate the video out ports.