MVP Sandi Hardmeier authored the Playing favorites: How to control which browser is 'Head Honcho' on your PC article, which begins with:

By nature, I am a very curious person, and have always enjoyed experimenting with different Web browsers. Tabbed browsing, for me, was never reason enough to change default browsers, but pop-up blocking and protection from malware was.

Now that Internet Explorer has a pop-up blocker, an Add-On Manager, and improved protection from potentially harmful downloads, it’s getting harder to find a reason to not use Internet Explorer. Add to that the fact that Internet Explorer 7 is not far away and promising some fantastic improvements, and I anticipate that some people (including me) may want to give the new version a go and revert back to having Internet Explorer as their default browser. So, let’s have a look at how to swap between different default Web browsers.