Here's the procedure for installing IE Tab:

1. In Firefox go to Tools, Add-ons, and click on Get Extensions in the lower right-hand side.
2. In the Search box, type "IE Tab."
3. Install the add-on and restart your browser.
4. Now you can configure the Web sites of your choice (e.g., Microsoft.com) to run under IE instead of Firefox.

Keep in mind that using IE Tab is just like running IE, even though you're using Firefox as your browser. In other words, you won't be protected from the vulnerabilities that exist in IE.

To protect myself, I use another Firefox add-on called "User Agent Switcher." This add-on doesn't use the IE engine; it simply fools Web sites by reporting itself as IE. Web sites such as Windows Update are happy that your browser is IE -- even when it isn't.