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If you do Web design, and who doesn't these days, then you might be interested in seeing how your site operates in multiple browsers. You could, of course, create a virtual machine for each version of Internet Explorer that you want to test against. But there's a better way.
There is a repository of standalone IE versions all the way back to 3.0. Tredsoft has an installer that will install any or all of these in one convenient package. A few minutes after starting the download, I had IE6 up and running in all it's, ahem, glory. IE7 runs right along side without a hiccup.