you have to go to add file from itunes on new ibook and highlight all the music you want to copy. your purchased music will not move over.
im not 110% sure this will work for you, but this is what i did. i deleted my downloaded music (the protected aac files from my old comp) then i went to my ibook and went to advanced -> check for purchased music, and it downloaded it again to this computer. there may be other better ways to do it but that is what i did when i moved from my pc, to my ibook. good luck.