I keep trying to play a DVD on windows media player but it says that I need a dvd decoder

I've tried downloading several multimedia players like DivX and VLC
none of them will work
I also downloaded the plug-in that it said to download: nothing.

I don't know what to do.
And we will weave in and out of sanity unnoticed
Swirling in blissfully restless visions of all our bleary progress
Glowing in radiant madness