suzi2

You could try using SourceForge.net: massid3lib - Mp3 Tag Tools

It is from Sourceforge which is a group of people developing free and mostly very very good software.

Or Mp3tag - the universal Tag Editor (ID3v1, ID3v2, APEv2)

There are many others available but these two seem to be among the best!
And, remember to first practice on COPIES of your files whenever using any new software that alters your files!

You might want to have a look at SourceForge.net: Files also because it does some interesting things with changing and renaming many files at the same time - in case you ever have any problems with a virus changing the .mp3 extension name to something else like .exe or whatever. Hope that never happens to you!