I have recently found a way to install all versions of Internet explorer on my PC. There are ways to do this using both freeware and paid applications, but my favorite thus far is a little program by Trendosoft which has an installer which contains IE3, 4, 5, 5.5 and 6. You can select some or all of the versions of IE you want to install and then it creates shortcuts on your  desktop based on your selections. This is a great tool to use for checking  cross browser compatibility and best of all it is FREE!