If you can’t get mp3tag to work you can always do it yourself manually. In Win xp, just right click on each mp3, select properties, click the summary tab and then click advanced. From there you can edit whatever you want, e.g. artists name, song title, album, genre, etc…
This works about the same way in Vista. You just right click on the mp3 and select properties and go to the details tab to adjust the mp3 info.
I do this very often and my Clip recognizes everything I input this way every time.