Mp3tag worked happily, but I got new problem after the work.
1. Windows backup skipped audio file directory I worked with and appear error code 0x80070002F.
2. So, I removed covers form all *.mp3 files.
3. Then, I tried "Windows Backup" once again, but same error occurred.
4. Next step, I moved all cover art files *.jpg files from my computer to removal USB storage.
5. In spite of no art cover files in my computer, each artcover will appear when it is played under Media Player.
6. I can not see any information about cover art in the file property.
7. Then foolishly I tried to convert the file from *.mp3 to WMA2, but result was same.
I have no further idea to try something.
Looking forward to the pleasure of hearing some hints or idea from you.