Here's how my friend is able to hook up his old laptop to the tv. He's got a DELL I5000 running Win2000 with a ATI Rage Mobility P video card.
I don't how helpful this will be but hopefully it'll lead you in the right direction.
View Display Properties
(Right click on Desktop>select Properties>select Settings>select Adanced>select Displays)
Select the TV option
(If your S-video cable is properly attached from the pc to the tv, then this option is already selected. On the upper left hand corner is a colored circle. This is the enable/disable button. If it's not colored in, then Click once on the button so that it is. Uncheck the button that reads Secondary. Once unchecked, the button should now read as Primary. Select OK.)
That's it. The computer screen is now displayed on your tv monitor.
Again hope this helps. If not, at least take heart in knowing someone responded to your post. I'm still waiting for a response for my problem.