Here is a question asked about how to backup and saving DRM Purchased Music:
How do you backup the DRM music you purchase? I’ve noticed that Windows Media Player 11 included with vista doesn’t include an option to do this like in previous versions. Would using the backup and restore program and selecting your music save both the music and your license?
As far as I know, there is no such good software to help you backup both DRM music and license for you.
But that doesn’t means we have no solution. Since restrict of the DRM.
The solution is using some software to remove protection from the music files you want to saving and backup.
Now come to the tool:

Digital Music Converter
Digital Music Converter is powerful yet easy-to-use protected music converter software. This excellent DRM removal software provides professional DRM removal mechanism, so you can remove DRM from protected music such as DRM WMA, DRM WMV, DRM ASF and M4B, M4P, M4V(iTunes) to plain MP3 or other popular audio formats. Due to its optimized DRM removal engine, you can efficiently convert DRM protected music with high quality.
Then you can use this software to help you saving DRM purchased music to wherever you want whenever you want.
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