m4a is a different kind of compressed file. I personaly dislike everything ipod represents and is attempting. You need to convert your files into mp3 from your original archives.
Some m4a files are encoded with DRM which prohibits such conversions if you purchased your stuff from itunes store. For this reason, many people buy the Physical CD and ripps them into mp3 just like I do. From now on, get your stuff physically and do not rely on digital downloads. Your basically not owning it and you are just renting it. Missrepresentation of this will go into courts sooner or later as soon as people can get a clue what is really going on. Anyway, Easy CDDA has a file converter so you can cross ripp your m4a files into something else.
http://www.poikosoft.com/ this software is not free but i just love it. do your homework and do some research... on file conversions.
here is a free one
http://www.mp3-converter.com/cdda_xtractor.htm it uses lame and if you install it, you might need to install lame encoder which is opensource mp3. make sure your ripper supports id3 tags for artist identification.
I think you can also tell your itunes to ripp into mp3 instead of m4a. Not sure because it just really sucks.
so three things you need is in a ripper
1. mp3 ripp
2. cdda lookup to identify the cd and label the album tracks
3. id3 encoding.
the cdda xtractor which is free from the link i provided does that, you may need to tweek it so you can ripp to mp3.
of course your itunes will not work with this because, you need to tell your itunes where you ripp the albums too. really sucks.