After shifting to a new version of Windows, Windows 7, which comes with Windows Media Player 12, I found that sometimes, WMP12 does not read the tags properly, e.g. displaying Unicode tags as garbage, or still able to display tags, but in garbage when I have used Mp3Tag to remove all tags from the file. However, this only happens if the files are not in the Music Library, hence not indexed by WMP.
After much self-research, I think I might have found the root of the issue, and how to solve it. For some reasons which I have no idea of, some MP3 files contain garbage data within the file, which normally unrecognized by players, including Mp3Tag. Windows Media Player 12 decides to pick those garbage data up and display it (I have no idea why).
What I've done is, I used Mp3Tag to remove all the tags in the file, and open the file using a hex editor. I can see there are still some track information retained in the beginning of the file, which I believe is what WMP picked up.
So I've used this little tool, Mp3Val and scanned the mentioned file, and it gives me a 'MPEG Stream Sync Error' when there are tags in the file, and 'Garbage data at the beginning of file' when I removed all the tags. The tool I mentioned is able to fix that problem by removing the garbage data, and after that, WMP does not pick the garbage tags up again.
I would like to suggest incorporating the function of MP3Val into Mp3Tag, optionally automatically scan the files for error upon tag editing, and fix it if possible. The mentioned tool and it's source code can be obtained from http://mp3val.sourceforge.net/
If you would need a file for testing purposes, I would happy to provide one.
Thank you for your time.