Unless there is some other topic about this option, I was thinking about
In
Properties > Security > Groups or authenticated users
I have 4 entries:
1] Authenticated Users
2] SYSTEM
3] Administrators (NAME-OF-MY-MACHINE\Administrators )
4] Users ((NAME-OF-MY-MACHINE\Users)
The 1 lacks for files Full control while the 4 lacks Full control, Modify and Special permissions. But changing these to Allow does not help- Mp3tag still behaves in the same way [I have that file format o the list and yet I do not see such files in the main window]