This may be a stupid question, but while tag information from iTunes M4A files is clearly visible in Mp3tag (and other tagging proggies) they do not show up in the details columns of Windows Explorer. MP3 file tags *do* show up and can, in fact, be edited from within Explorer by simply right clicking on the file and selecting Properties->Summary->Advanced.
Does anyone know of a way to make tag information from M4A files available to Windows Explorer short of doing the unthinkable and converting all the damn things (I have close to 2,000 of them) to MP3 format?

Windows Explorer makes use of some Windows Media Player APIs which are responsible for reading ID3v1 and ID3v2 tags. MPEG-4 files don't use any of this tags, instead they have their own tagging system.

Anyways, you could try out this software: http://forum.dbpoweramp.com/showthread.php?p=13763#post13763