Sharing my own experience, hope it helps somebody.
I'm an iTunes subscriber and I have gigabites of iTunes M4P files on my machine. Of course I listened to them on iPod. But recentluy my iPod was broken (sh*t!) and I've got a new zune player on my birthday! Obviously I couldn't transfer my M4P collection to it because these file had iTunes DRM protection. Luckily I found
MP4 converter and converted all my iTunes files just in few clicks!So I would recommend this
MP4 converter if you have any problems with iTunes files - it can 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