I know that the information that WMP uses to populate the Media Library section is all held in a file called wmplibrary*.db which can be found in %allusersprofile%\application data\microsoft\media index (which by default is C:\Documents and Settings\All Users\Application Data\Microsoft\Media Index). I can't try viewing this file on the machine I'm typing this reply on, but you might wanna see how you can view/extract the contents of this file.
ps - for an interesting read about WMP and your privacy, check
http://www.computerbytesman.com/privacy/wmp8dvd.htm