Microsoft are heavily promoting their new "Edge" browser, to the point where we are unable to stop it from being your initial default browser. You can choose to make one of your other installed browsers the default by using the instructions specific to them (e.g. Internet Explorer, Google Chrome, Mozilla Firefox).

There may be instances where Microsoft Edge takes back file and URL associations unexpectedly - this is a known feature of the browser and currently the only fix is to repeat the steps shown above.