"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."
As soon as I got an internet connection, I tried downloading a driver for my video card. After installing it, I assumed that the DVD would play (after all, the message told me it would!).
No luck. I then downloaded new firmware and drivers for my DVD drive. The message did say something about my DVD drive too ...
Again, no luck. Well, what else is there? Then I noticed the word 'decoder' in the message and decided to pursue that option.
I tried a few things, but the one that actually did the trick was to download the XP Codec Pack. After downloading and installing these codecs, I was finally able to play the DVD that we brought to occupy our time on our short road trip!