mp3's are not protected per se AFAIK. WMA & m4p files were files purchased over the internet & have protection to prevent them being burnt by other people. These files should not be shared but some do.

I'd suggest you try to stay away from wma & m4p files. m4a files are generally ok. And besides, over a year ago Apple supposedly dropped their DRM restrictions on their online files hoping others like M$ would do the same.