It's an XML file, hence the extension. It can be viewed with Notepad if desired, or even MS-Word, as XML is at its heart a formatted text layout.
Its sole purpose is to select an existing Windows ring sound that I've not seen used elsewhere unless someone selects it elsewhere and using it for the sound to be played when the event is triggered.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
The real art of conversation is not only to say the right thing in the right place but to leave unsaid the wrong thing at the tempting moment.
~ Dorothy Nevill