This is just a small utility to help with backing up my music files. It's by no means perfect or complete, as I wrote it in a few minutes, but it might be of use to someone and posting it here might motivate me to improve it.
The idea is to have all CD contents in files generated by tree e: /A /F in Windows. Then running this program against a directory of music files will print out the ones requiring backup, i.e. the ones not in any of the CD listings.
View Source | Download Utility (right-click & Save Link Target As...)