Converting MPEG-4 Audio File (Protected) to MP3

New user purchasing tunes for my Lyrica MP3 player using daughters setup for IPod. Tunes downloaded in MPEG-4 audio file format and are 'protected'. When trying to convert to MP3 it won't because of its protected status. How can I convert them? If I already purchased the songs, can I go back and download them again in the MP3 format? Did I just waste my gift card and need to purchase them all again downloading them in MP3 format? Thanks

Windows XP