I wrote this a couple of years ago on a Creative decoder that I don’t believe is available anymore:Creative CT7160 Dxr2 Decoder Board. Not required if you don't include the DVD drive. Software decoders come with many higher-end video boards and is included with the Diamond board used in the example computer. A hardware decoder is faster. Furthermore, the Creative decoder has TV and S-video outputs. Creative has a newer decoder board on the market, but the one used in the example machine is readily available, coasts less, and works great.
Other decoders should be available. It might be cheaper to buy a new display adapter. Larry