Windows Media Player Cannot Play This DVD Because There Is a Problem With Digital Copy Protection

What Digital Copy Protection Is
Digital Copy Protection is a system that protects the contents of DVDs from theft. Unscrupulous users will sometimes attempt to copy the DVD and then burn its contents to other discs. They would then attempt to sell or distribute the disc themselves. Digital Copy Protection protects the contents of a DVD by encrypting the data and requiring that any person or software program attempting to access it has the proper key. This ensures that only approved media players will be able to play the DVD.
Video Codecs
A video codec is a small program that executes within a media player. This program contains the keys required to decrypt various types of video encryption. Without this codec, a media player simply will not be able to open many types of video files. In fact, this is the source of many errors given by media players, and specifically the error regarding Digital Copy Protection.
Microsoft's DVD Troubleshooter
A good place to start when attempting to diagnose Windows Media Player errors is Microsoft's DVD Troubleshooter. This is a small program that is integrated with both Windows XP, Vista, and Windows 7. The Troubleshooter will give you a list of symptoms to choose from and will then suggest fixes based on your selection. To access the troubleshooter in Windows XP, click 'Start' and then click 'Help and Support.' Point the mouse cursor to 'Pick a Help Topic' and then click 'Fixing a Problem.' Next click 'Games, Sound and Video Problems' and then click 'DVD Troubleshooter.' To access the Troubleshooter in Windows 7 or Vista, click 'Start' and then type 'Troubleshooter' in the search box.
Downloading Codecs
A situation may arise in which Windows Media Player does not have the required codec installed. In such a case, the media player will give an error message if you try to play the video file. However, there are several codecs available on the Internet that can extend the functionality of most media players. These codecs are often free of charge, and a popular example is the MPEG-2 codec. However, it is a good idea to use caution when installing files from any source. Always download from trusted sources.