the best thing to do is not to rip in AAC in iTunes. under preferences you can tell it to rip in mp3. there are apps out there that can crack AAC protection but i think they only work up to iTunes 4.3 or something.
you should be able to right click a file in your itunes library and select "convert selected to mp3". If the option is not there, go to
edit --> preferences click the advanced tab then the importing subtab. change your "import using" to "mp3 encoder"