I use a utility called "Sandboxie" (free for personal use, $29 for commercial) to provide application sandboxing. One useful side-effect of this is that you can install applications (even OS-modifying ones such as IE) into the sandbox, and the parent OS is completely unaware (allowing you to have different versions of the parent OS's IE and the sandboxed IE - and both running simultaneously). The two scenarios I've used so far:
- Internet Explorer 7 in the parent OS, and uninstalled IE7 in the sandbox to make IE6 available
- Internet Explorer 6 in the parent os, and upgraded to IE8 in the sandbox
Caveats:
- If you need more than one additional version of IE available simultaneously, then you will need to purchase the full version, as you can only have one version of IE in a sandbox, and the free version supports only one active sandbox at a time
- Installing a version of IE into the sandbox can take a little trial and error - IE8 was particularly tricky. Some warnings that occur during installation (or uninstallation) are trivial, though.
