There are also no utility to access and repair or export/import the library database, which I believe also contains the artwork, that's why deleting artwork files or the art cache does not affect matters.
That's not entirely true - the library doesn't contain any actual artwork data, this is only stored in the separate JPG files or embedded into the music files themselves. Only the link to the JPG files (the GUID in their filename) is stored in the library.
Possibly, but it amounts to the same effect, if not the jpg itself, the GUID in the library database will restore the wrong artwork as soon as you connect the library to Internet. I couldn't find any documentation about the WMP library internals, so I'm left to guesswork...
And there is no way I can see that my corrected album information can be pushed back to the Microsoft album information servers. Many albums outside mainstream pop and rock have incorrect information, typos in the song names, classical music frequently does not have any track name or have track names written in Japanese, etc.
Did you enter the corrections in the library itself? If you enter them through the Find Album Info wizard, then they should be used to correct the database in the future, see
WMP FAQ: A trouble-shooting guide for Windows Media Player problems.
The wizard is really not usable when you rip dozens of CDs in one session. I frequently need to fix the artwork, album and artist information too, so I enter all the corrections in one place, directly in the library. Well, 2 places since I also frequently need to rename the track file names in Windows Explorer because WMP stupidly does not rename files if only the case is changed.
There are multiple methods of entering music metadata, like in the file properties from Windows Explorer, so obviously you can't elect a single method like the wizard, it's the library itself that should detect
any change and push them back to the servers.
Nobody is running the whole wizard when they notice a track name has a typo in it, they just fix the typo in the track name that's displayed, and nobody is aware that the information is sent back only from the wizard.
Why would anybody use the wizard anyway? Either the album information was already found, or it wasn't and you need to enter it all, which the wizard can't do.
I have several playlists I can't remove from WMP, because I made the mistake of deleting the playlist file in Windows Explorer instead of in WMP. So they point to files that don't exist, but WMP is too stupid to notice and let me delete them.
Resetting WMP's library should get rid of the orphaned playlists, see my answer in
this thread for full instructions.
This is not an option, I spent many man-days over many years fine-tuning my library, and the library contains metadata that's not in the audio files or folders and is used by other apps such as LastFM.
I'd rather have WMP be smarter and delete playlists that don't exist on his own. That's really the basics and can't be difficult. If you can create playlists by copying playlist files to the music library folder in Windows Explorer, it stands to reason that you should be able to delete the file in Windows Explorer as well.