I'm here, with a great heaviness in my heart, to tell you that Windows 7 WMP completely trashed my 1.5 TB MP3 library. I started it up, pointing it to a network watch folder and saw it doing some good things, organizing my library and gathering additonal info on incompletel files. Unfortunately I left it running overnight, and found extensive destruction to my file names and tags. Specifically, WMP took tracks from a single album and renamed them the wrong names. The file names were changed and the metadata was changed, usually creating duplicates, and oddly often duplicating odd numbered tracks. So what once were tracks 1 through 8 for example, often became duplicates of tracks 3, 5, and 7.
Fortunately, the folder structures were not renamed and as far as I can tell the files were not moved to album folders of the wrong name, so I think I can write some software to get out of this mess. My folder structure goes "Artist/Album", so I am hoping I can inspect those folder names, then gather the track lengths and compare against the actual tracks in the album and put things back.
What an incredible disappointment.