Elfcall, WMP has removed all tracks from the library all by itself, and I have never put songs into the player, playing them directly from the library. I am tempted to see if I can load the WMP library from the MM library, because MM hijacked most of its content from WMP in the first place.
At the moment I'm filling a MP3 player, and the MP# converter that I'm using (Free CD to MP3) turns CDs into WAV files at the same time as MP3 files, so that is a start in the refilling process.