You need a VGA to S-Video/Composite adapter thing, like this:
USB Powered VGA to Composite + S-Video Converter Box (1280*1024px Max)
Look around. There's a lot of different ones out there.
As long as the TV has some sort of input, you can output your computer's video to it. I did that with my parents' late 80s Zenith (the 'wood' box ones).