I think the letters dnp were mentioned when I researched the subject. I was warned to be careful about where and what kind of decoder I should obtain. Any suggestions/
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A DVD Decoder was not included with Windows XP...
so one has to be acquired and installed from a third
party source. If your system had one when it was new...
it would have been included in your OEM software
package...maybe you still have the install disk for it.
The following site has some suggestions:
Info on DVD Decoders: Plug-ins for Windows Media Player
http://www.microsoft.com/windows/windowsmedia/player/plugins.aspx
And...maybe the freeware VLC Media Player would be
worth a try...it will play just about anything.
(FWIW...it's always a good idea to create a System
Restore point before installing software or updates)
VLC Media Player
http://www.filehippo.com/download_vlc/
(runs on XP/Vista/7)
(the filename to download is : vlc-2.0.2-win32.exe)
Good luck...