To reset the DRM system, do the following:
This will delete all media usage rights and you will not be able to play any protected files until the new media usage rights are downloaded. Microsoft Recorded TV Shows (DVR-MS files), however, will be deleted and cannot be replaced.
Verify that Windows is configured to show hidden files and protected operating system files.
If your computer is running Windows XP Media Center Edition 2005, you should also stop the Media Center receiver service by typing net stop ehrecvr at a command prompt.
Open the Windows Media DRM folder. This folder is usually at C:\public\DRM.
If you cannot find the DRM folder, do the following:
In the Windows Media DRM folder, select and delete all of the files, and then restart the computer.
To download new media usage rights for a file, start the Player and play the file. The Player will contact the online store and attempt to download new rights.
If you want to download rights for a lot of files, you can also contact your online store to find out if the store provides the ability to restore or renew rights for all files that you have obtained from the store.
For information about resetting DRM for Windows Media Player 10, in the Microsoft Knowledge Base, see article 810422, "'Licenses for your media files are corrupted' or 'License is either corrupted or not valid' error message when you try to play licensed media files."