I want to hook up a Toshiba laptop to a Panosonic rear projection

VGA, and supervideo only carry the visual signal, so if you use one of this cables, (both the computer and the tv have to have the same output/input) then you have to have a cable attached to the computers audio output to carry audio to the TV. If your computer has HDMI output and the tv has an HDMI input, then that carries both visual and audio. When you attach the video cable to the tv, put the tv on that input source and the computer will sense the device and if the drivers are updated will fire the signal up automatically and give you the choice of using only the tv, or using both the tv and laptop monitor.