This is handy for when you need to test a website out in multiple versions of Internet Explorer. And its free! Windows only, but then again, IE for Mac is out of development, so its less of an issue. Installation is a breeze, and I’ve set it up on several systems without so much as a single glitch. No promises for Vista tho – I refuse to install it, so I can’t vouch for anything running on it.
Get it free at tredoft.com.