You'd get better replies if you posted your graphics card make and model. And types of output supported by your sound card/onboard audio.
Too bad you don't have a S-Video in on your TV. S-Video to Composite adapter cables mix chroma signals with luminance signals causing inferior picture quality. This results in noticeably bad text and colour bleeding in pictures.
This article should answer most of your queries -
*www.weethet.nl/english/video_connect_pc2tv.php
Try to connect optical out of your soundcard/onboard audio to your home theatre reciever.
-Keith