Standalone IE 5.1, 5.5, & 6
Anyone who uses CSS based design knows about the joys of IE compatibility. I just recently set out to find older versions of IE to test my sites compatibility with the older browsers. It’s next to impossible to run parallel installs of different versions of IE because of its integration into the OS, but why install when you can run it right out of the box, install free? Attached to this post is a zip file containing IE 5.01, 5.5 and 6. This will allow you to install and start testing version 7 but still be able to refer back to previous more common versions until 7 hits the mainstream.
There is a fantastic old browser archive located here: http://browsers.evolt.org