Napster music contains DRM protection, which always in a DRM protected WMA format. If you want to put it into iPod, Zune, or other MP3 player, you have to remove DRM protection from Napster music first. Here is a detailed guide to show you how to remove Napster DRM.
You may need specific Napster DRM Removal Software to strip this DRM copy protection from these Napster WMA tracks. This article presents you a easy way: using software, such as Wondershare Music Converter to remove Napster protection to non-drm ones . This software is especially useful for alleviating compatibility issues.
More info,kindly refer to this tutorial : http://fast-remove-drm.blogspot.com/2009/12/how-to-remove-drm-protection-from.html