
This sets the file type association in Windows.
If you click on an audio file in Explorer it will open JRiver.
If you set the association this is what you see Explorer

All file types are set to Media Center File.
No way to tell the difference between MP3, FLAC, etc. anymore in Explorer.
This is a very annoying trait of JRiver.
I have a very simple if a bit blunt solution.
Associate the file type with Foobar or WMP.
In Control Panel > Default Programs

Choose Associate a file type or protocol with a program

Choose an audio file like FLAC and double click.

Choose any program not ruining the extension.

E voilà!
File Types Settings - JRiver Wiki