VirtualBox Windows guests to run IE on Mac

When I left my "corporate job" (in order to start my own corporation), I also left behind (if only temporarily) Windows in favor of my trusty MacBook (and my even trustier Mac Mini server). But of course, I still need to test on Windows from time to time, and so I've been using VirtualBox with some Windows guests. The best way to wrangle that is from this 2011 article: Internet Explorer for Mac the Easy Way: Run IE 7, IE8, & IE9 Free in a Virtual Machine.