Hi ben71r,
3 ideas
1. As you open the file and go properties, uncheck the read only attribute.
2. Back the file up and on the backup version 'Remove Properties and Personal Information', can you now edit it?
3. Try the take ownership script that I have attached in the ZIP file. Merge it, then right click on teh mp3 and select 'take ownership', now try to change it. You can remove this functionality with the second reg file in the zip folder.
lastly, try