If you run Windows, there is no way to have two versions of Internet Explorer running at the same time without using special software.

Unlike Netscape, Opera, and other browsers, Internet Explorer 4+ shares resources with Windows making multiple versions almost impossible. Installing emulator software, like VMware, to run multiple versions of Windows will work, but is a resource drain (to use VMware, you need Windows NT 4.0, Windows 2000 or Windows XP).

Another option is to partition the hard drive and install multiple versions of Windows, each with a unique version of Internet Explorer.