Hi,
This is a problem I've seen in both WMP and iTunes. The real issue is with non-purchased music in your library. Lots of music that's copied from public sources such as uTorrent and Pirate Bay don't have good copying software (as this is done by people on their home computers), and they don't get all the attributes of MP4, AAC, MP3, etc. necessary to include the Album art. There are free programs out there that attempt to correct this, but none I've seen do 100%!! An example of this is FixTunes for iTunes, which does a pretty good job on pilfered or non-purchased music.
To fix this problem, delete
ALL your music from your hard drive after backing up to external media first (if you haven't done so already). Then, log into whatever online account you have used for your purchased music (such as iTunes Store, GooglePlay Store, Amazon Prime, etc.). Do a 1-way or a Synchronize command once you open up your WMP; and all of your previously purchased music will magically download into your WMP library with the correct Album art pictures and track titles!
Things in version WMP 10 and above should work fine then.
If you have
NO purchased music whatsoever, there are no tools I've seen that compensate for DRM protected music that put back or repopulate Album art 100% for publicly available music/albums. Sorry about that! If you want to see this work for yourself, follow my procedure; remove all non-purchased music from your computer, and setup an online account with iTunes or one of the other legit music online retailers; spend $10 and download a legit album into WMP, and you'll see that it works.
Good luck to you,
<<<BIGBEARJEDI>>>
