s-video connection / output to TV set

hi i have a connection for an s-video cable in the back
of my computer and i'm wondering how to get it to work.
the goal here is to have my desktop displayed on a
television screen. i know the s-video cable works, i've
done this successfully with a laptop using the same
cable, but for some reason i can't get it to work with my
PC.

if anyone knows if there is some button i need to press
or a setting somewhere i need to change so the output
will go through the s-video cable please let me know here
or email me.

i appreciate any and all help with this issue.

thank you