Using a special VGA to RGB Scart cable you can use a normal VGA out on (some) videocards to display a image on a TV.
WARNING Please be carefull with these kinds of cables. Incorrect use of the cable and/or setting in your operating system can (potentially) damage your TV
2 Types of cables
There are 2 types of cables. Cables for Radeon videocards that can output a correct signal directly, and cables with some circuits to change some signals.
Here are some links to information on how to convert the VGA out signal to a suitable signal for a RGB Scart input.