Browser Compatibility Check for Internet Explorer Versions from 5.5 to 8
 

Alpha software but potentially useful.


IETester is a free WebBrowser that allows you to have the rendering and javascript engines of IE8, IE7 IE 6 and IE5.5 on Windows 7, Vista and XP, as well as the installed IE in the same process.

http://www.my-debugbar.com/wiki/IETester/HomePage