After a fresh install of 2.73 (tried 2.73a also) on a newly built Windows 10 PC, I set "File > Options > Directories > Favourite directory" to "E:\Music".
Both the "Subdirectories" and "start from this directory" checkboxes are ticked, but when I start mp3tag - the Directory it tries to read music from instead defaults to the install directory "C:\Program Files (x86)\Mp3tag".
If I change the "Favourite directory" setting to "E:\Music" and restart the program, it opens and starts reading tags as expected, with Directory displayed as "E:\Music".
There is likely a better way to set mp3tag's starting directory (leaving "Favourite directory" blank and using "File > Change directory" probably), however using the method I used, I think that both "E:\Music" and "E:\Music" in the "Favourite directory" field should produce the same results.
The optional favorite setting "E:\Music" is the same as Mp3tag displays in its window header line, which looks ok for me.
Do you see the missing trailing backslash in the Tag-Panel window?
I think we have discussed this topic already, ... and I support this wish, that the current directory path string should have the trailing backslash also in the Tag-Panel window.
I've attached one screenshot showing the program after startup with Favourite directory set to "E:\Music" (blank results - reading from Program Files instead) and another screenshot showing the program after startup with Favourite directory set to "E:\Music" (correct results).
The problem isn't so much what displays in the window header line or in the Tag-Panel window; it's more the fact that the wrong directory is being read when the trailing backslash is not included in the Favourite directory setting.
Even if I forcefully remove the trailing backslash in the path of the default directory, MP3tag adds it and therefore opens the correct folder.
Yet: the tag panel shows the same path without backslash in the field for path ...