this is not really the same thing, but it can help:
"Install multiple versions of IE on your PC"
http://tredosoft.com/Multiple_IE
It hasn't been updated in a while, I really only use it to be able to run IE6 alongside IE7 (which i have installed in the normal way) for testing purposes.
Unfortunately, installing both IE6 and IE7 on the same machine causes IE6 to mishandle cookies, among other problems. You won't be able to log into many sites (Drupal sites, for example) when using this method.
It hasn't been updated in a while, I really only use it to be able to run IE6 alongside IE7 (which i have installed in the normal way) for testing purposes.