Sharing my own story, hope it's helpful for somebody.
Ihave an iTunes account user and I have gigabites of iTunes M4P files on my hard drive. Of course I listened to them on iPod. But recentluy my iPod was stolen (sh*t!) and I've got a new mp3 player on my birthday! Obviously I was unable to transfer my M4P collection to it because these file had iTunes DRM protection. Fornately I found MP4 converter and converted all my iTunes library just in few clicks!So I recommend this MP4 converter if you have any problems with protected files - it will convert them to unprotected MP3 or any other format so you can use them on any player or PC.
The url is mp4-converter.info or something like this. Tell me if you need exact will go thru my mail