Upload songs problem (M4a files)

I uploaded some hard to find music to the network and realized after that they are m4a files instead of the usual mp3 files. Blue stars usually appear next to a mp4 file, when you click on them it opens up itunes and plays on itunes as well. Just wondering how I can convert these m4a files to mp3 files. after all if someone doesn't have itunes then they cannot play these files i believe

Don't transcode files unless from a lossless source. transcoding m4a -> mp3 will give really bad results.

People that wan't m4a will download it, and people that want mp3 can download some other copy.