How do I make Firefox my default browser?
To make Firefox your default web browser:1. Select Tools > OptionsEdit > PreferencesFirefox > Preferences and click the “Check Now” button in the General panel.
When setting a computer to use Firefox as the primary browser, it is helpful to disable Internet Explorer’s checks to make it the default browser:
Start > Settings > Control Panels > Internet Options > Programs > Internet Explorer should check to see whether it is the default browser