How can I set the default browser on my computer back to Microsoft Internet Explorer (IE)?

By default, IE checks whether it’s the default browser each time it starts. If you disabled this check, you can reenable it by performing these steps:

Start IE.
From the Tools menu, select Internet Options.
Click the Programs tab.
Select the “Internet Explorer should check to see whether it is the default browser” check box and click OK.
When you restart IE, you’ll be given the option to make it your default browser.