Microsoft SuperPreview: Testing Multiple Browser Versions
It's been either hard or expensive to test websites in different versions of Internet Explorer, espically if using host file entries for development.
Today Microsoft announced Microsoft Expression Web SuperPreview, which will allow developers to compare different IE, Firefox, and Safari versions using cloud computing. Additional features include side-by-side comparisons, browser size reviews, alignment checks, DOM checks, and an almighty overlay review and more.
For now, you can download the Microsoft Expression Web SuperPreview for Windows Internet Explorer for free from Microsoft. This is a pre-release of the free version and tests IE 6 and 7, plus 8 if you have it installed. (Note: take the usual beta software precautions).
I've also run into others such as DebugBar's IETester.
This is a way to install multiple versions of IE in stand-alone mode. I use this all the time for testing. I run IE7 full and test IE6 in stand-alone mode. This is becoming an outdated solution though.