How to playback DVD?
DVD is based on MPEG2 format. Windows for various reasons don't come with a standard MPEG2 decoder, even though MPEG2 has been around for quite some time. As a result you need to buy a MPEG2 decoder, or use one of the open source alternatives. If you are running Windows XP, there are several decoders with pretty low price points available from Windows Media Player's plugin page. Another good DVD decoder is NVIDIA's PureVideo Decoder. You may also purchase full versions of DVD player such as PowerDVD or WinDVD, which come with MPEG2 decoders. However, some decoders may only work with its own DVD player, or Windows Media Player, so just beware. A nice open source MPEG2 decoder is DScaler.