Windows Media Player cannot play this DVD because there is a problem with digital copy protection between your DVD drive, decoder, and video card. Try installing an updated driver for your video card.

I now never bother with anything other thanVLC as it does everything I requireand better than WMP.

 My main gripe was that it gave the same message for my own DVDs so DRM shouldn't come into it! Burned on PC or DVD recorder, same thing. As everything plays on the old Microsoft player I could use that but why bother. If Microsoft are so paranoid that WMP refuses to work if you have other (legal and legitimate) programs you have used with previous versions of WMP (as I said, my DVDs were playing fine until the suto update came along, installed itself and when I tried the watch the DVD I was half way through this happened - only stopped watching because I had to reboot the system for the updates to work) there's something very wrong. May well be something in the background that upsets it but it shouldn't, that's the point. Microsoft should have at least given a warning as, presumably, someone had thought about possible problems with other software, before they just went ahead and installed the thing. Not a word. That's bad testing but, again, that's \microsoft - we are all beta testers for them.

have you tried my suggestions and/or VLC?

I installed VLC player and it ran great.

I had this problem too (windows 7, WMP 12 it appears) with DVD's.

I believe it started in conjunction with me adding another drive to my system (?)

Anyway the fix that worked for me was (I think, anyway), to go to device manager (right click my computer -> properties -> device manager) and disable one drive. Then reboot. Now it works. Now re-enable the drive. Works from then on.  Weird.

Many other things that I tried resulted in the DVD being able to playback correctly *once*, then I would get the same message (ex: re-install video drivers.  DVD plays back once. Then error message again after that, or install a new audio codec, same deal. Weird.).

Other hints from the web:

"nero 8 maybe messes things up perhaps?" http://www.howtogeek.com/forum/topic/problems-with-windows-media-player

"maybe it is using the wrong audio driver" http://www.bleepingcomputer.com/forums/topic81860.html

"cycle a system setting, then it will play once, then cycle it again" http://answers.microsoft.com/en-us/windows/forum/windows\_vista-sound/cannot-play-a-dvd-in-windows-media-player/e78aff8d-d921-4576-bc23-12f5c5ec9388

"make sure all of your monitor devices are enabled" http://www.vistaheads.com/forums/microsoft-public-windows-vista-general/111615-please-help-windows-media-player-cannot-play-dvd-because-there-problem-digital-copy-protection-between-your-dvd-drive-decoder-video-card-try-installing-updated-driver-your-video-card-2.html

if you updated your DVD's firmware to some "region free" firmware, then flash it back to standard (also somebody else in this thread mentioned that flashing it to its latest revision helped them, above).

Removing daemon tools might help, too.

Also somebody above mentioned a way to re-install DVD drivers.  That might help, too.

A reboot in there somewhere might be required, too.

GL! (of course, playback with VLC or PowerDvd 8 always worked fine, just not WMP...weird).

-r

PS now I get pixelated jerky play the first time I play it, but the second time it works fine. Also weird. But at least it works.  Also related is http://social.msdn.microsoft.com/Forums/en/windowsdirectshowdevelopment/thread/77d75c54-d8d7-4616-907d-be627fc44bdc