Any reason it must be WMP?
Free to use at http://download.cnet.com/VLC-Media-Player/3000-13632_4-10267151.html
Any of the Windows DVD players will enable DVD play but your question was just the plug-ins. Microsoft writes about that at http://windows.microsoft.com/en-US/windows/downloads/windows-media-player/plug-ins
Hello..I wondered if anyone could suggest a DVD Decoder that is compatible with my WMP 11, so I can watch DVD movies on my PC? My operating system is Windows XP Prof. SP 3. Thanks for any suggestions you may be able to offer me!