Er... that ebay-listed cable above is for component output - separate red, blue and green signals. Your TV has to have matching component inputs for it to work. The Circuit City guy is sort of right, there isn't just a simple cable you can use to run VGA out to composite video, which is what your TV input is.
What you CAN use is an AverKey, which will give you fairly decent video, or get a video card with a composite output. AveryKeys are relatively expensive (new ones on the order of $200-$300, eBay will be cheaper - for example,
http://cgi.ebay.com/Avermedia-AverKe...QQcmdZViewItem) but they work quite well, as they're designed for presentation output from computers to TVs and projectors. We used to use them in a digital-arts school for instructors to show their PCs on the classroom projector... of course, this was before VGA input on projectors became very common.
You can also get a video card with a composite output, like my ATI Radeon9800 All-in-Wonder. It will work, but computer graphics won't look very good. If you're watching movies, though, and you're using a card that supports overlay mode (like the ATIs), video output will look just as good as coming from your DVD player (your biggest limitations will likely be in the quality of the source material itself).