If you’ve ever had to do any web testing, you’ve probably found that it’s a major pain trying to test out a site in multiple versions of IE, since new versions of IE tend to wipe out previous installs. I usually use a different virtual machine instance for different browsers and OSs I want to test, but this is difficult to set up and takes up a lot of disk space.
Yousif Al Saif put together a nice multi-IE package that bundles IE 3 through 6 into a single installer. Just make sure you have the latest version of IE first, then run his installer and it will create the other standalone IE versions, each with their own private set of DLLs and registry keys.
Install multiple versions of IE on your PC – Link