tag & rename, is what you want.
yup
http://www.softpointer.com/images/tr_main_full.png
it can do your whole collection in one go (i'd make a 2nd copy of your music folder, and run it on that, just incase)
it's not a player, it's just for renaming & tagging music
tag's are the data held in the file, such as Artist, Track Name, Album name, etc etc..
if you use winamp, hold ALT and tap 3 when selecting a song, it'll show you the tag..
never used wmp11, looked to bloaty, so can't comment