Scripting
You can access the object model of WMP.
A very simple way is to use VBS (Visual Basic Scripting)
This is a script exporting the contents of the library to Excel.
You can edit it using Notepad (or any other plain editor)
Run it by selecting it in Explorer and choose Execute.
If you remove the quote from this line: ' OldAlbum=Album
you get a list of albums instead of songs.
Windows Media Object Model Reference for Scripting
More objects: Attribute Reference
Examples: The Scripting Guys Really Do Rock