detecting a second monitor via s-video cable

I'm trying to connect my tv to my computer via s-video, but my laptop doesn't
seem to detect another monitor. I've tried plugging it in before and after
i've switched on the computer; tried 'Identify monitor' in display settings;
'graphics options' doesn't offer any solution that I can find and 'graphics
properties' doesn't come up with a 'monitor' option. Any ideas?
I'm using a Toshiba laptop, satellite p100-160
philips tv - an old one, but also tried a sony dvd recorder which is 3 or 4
years old