In Firefox menu:
Tools -> Options -> Advanced -> General -> System Defaults -> Check Now -> Would you like to make it your default browser?-> YES!
When IE ask for set it to default, answer NO and check Not check default browser in the future.
Tools -> Options -> Advanced -> General -> System Defaults -> Check Now -> Would you like to make it your default browser?-> YES!
When IE ask for set it to default, answer NO and check Not check default browser in the future.