Get hold of MusicMatch V4, it will convert your old files to ID3 tags, it also has the best music library around. I use it to organiz(s)e all of my MP3s.
It even lets you add stuff like cover art etc.
If you have loads of MP3 lying around, V4 will add all of the files starting at a path you specify. I have even paid for this product and keep getting the freebie updates.
And no, I don't work for them, I just like the product.
Mike