Normally, you can burn the protected music files to CD-R/RW disc. then rip them back to MP3.
There is a software "NoteBurner" from
http://www.noteburner.com can help to convert protected music to MP3 File by using a virtual CD-RW burning method. It works as a virtual CD-RW burner, after selecting "NoteBurner" as default CD burner, then the software will convert all the music files in playlist easily.
This seems like a AD, however, I use this tool and it did work.