Some of my music files in Windows Media Player did not show information about album, artist etc. I had them all in one section called Unknown album. I also found out that there are no meta tags displayed in the album’s folder.

To fix this I installed ID3-TagIT which was proposed on some forum.
After you install it. Open it and select a folder with corrupt files. then select all of the files which will appear. In the menu choose Extended Functions > Transfer/Convert TAGs or simply pres F7 key. In the dialog click on Convert TAG Ver. 2.4 to Ver. 2.3 and press OK. Finally save the changes. Missing information should appear in the music folder and tags should be OK also in the Windows Media Player.