http://tredosoft.com/IE7_standalone I just used the self-installer, and both versions of IE work perfectly on my computer. I also found a few glitches in my site, but fixed them thanks to this.
It really helps a lot. NOTE: This not a fully functional version of the browser, and some features will not work. For page testing, however, this will suffice.
But it's still necessary to test in IE7, as Microsoft will be forcing aggressive upgrades, not to mention the pending release of Vista.