How to replace m4a conversion files with original mp3 files in iTunes library to reduce disk space?

Question

Hello
I have a rather large music collection most of which is in mp3 format and also kept in seperate folders to my iTunes music. I had iTunes set up copy media to iTunes folder as m4a so now have two sets of files which are now taking up a large proportion of my hard disk space. Is there an easy way to move my mp3 files into the Itunes folder to replace the copies then delete the copied files.
Many thanks

Answer 1

By m4a are we talking compressed AAC?  Those don't take up any more room than the equivalent mp3 and probably give you better quality.
Are you positive those files are m4a?  If iTunes is set to copy media when you add it to the library I don't think it converts.  It only converts when you import.
Since we're not talking replacing mp3s with mp3s I don't know if there is an way to more or less invisibly replace the files.  If you were replacing a file with one of identical file name, you can trick iTunes into accepting it.  Since the new files end in mp3 and the old ones in m4a I suspect you will end up having to add the new files and delete the others.  This will of course mean you have to rebuild playlists and update tags.  Before you delete the old copy you can use Dougscript "Copy Tag Info Tracks To Tracks" to transfer some of the tag information that you might wish to retain such as playcount, ratings, last played, etc.