tv out from vga port Acer aspire 5102 wlmi

plese need help to conect regular tv from vga port (ATI radeon Xpress 1100) the laptop was upgrated to windows vista. I tryied using a VGA to composite cable staright to the video input on my tv but no images are recieved. Do I need to change any settings on the display mangeer or do I need some kind of special box converter?? thanks