If you've given up on trying to locate a working past library then you can add both iTunes Media and iTunes Music to the library you have now.
Under Edit > Preferences > Advanced make sure that the media folder is given as iTunes Media and both options Keep... and Copy.. are ticked. After adding both folders you can delete iTunes Music as these tracks will have been duplicated in iTunes Media folder. On the off chance that process also creates duplicates in the library I have a script DeDuper that can tidy up.
The steps above would temporarily double-up on the contents of the iTunes Music folder. If you don't have room for the additional copies turn off the Copy... option before adding to the library, then my script ConsolidateByMoving does just that.
If you want Windows Media Player and iTunes to share a common media folder see Getting iTunes & Windows Media Player to play nicely.
If you have any Apple device there are two more scripts of mine listed towards the end of Recover your iTunes library from your iPod or iOS device which can be used to recover ratings, play counts, and playlists. You should backup any iOS devices and then restore them to make sure the devices are properly tied to your new library.
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