There was an artical on ExtremeTech about AAC:
http://www.extremetech.com/article2/...1525987,00.asp
and a follow up artical:
http://www.extremetech.com/article2/...1549873,00.asp
I believe AAC from Apple (downloads) has a DRM formatting called Fair Play, and you can't JUST convert it to MP3. All you really can do is write to a CD, then rip that to MP3 (or whatever format you'd like).