If you ever been working on layout and design of website then you may need to test the layout and rendering of the website in different browser, like IE 7, IE 6, IE 5.5, FireFox, Opera, etc.
But normally it is not possible to install multiple version IE in same system. So to get through this limitation of Windows, I found the following program using this you can run multiple version of IE (IE 7.0, 6.0, 5.5, 5.1, 4.0, 3.0) in the same System,
Normally this installer will not work with Windows Vista,Follow the progress of running Internet Explorer 6 natively on Windows Vista here!
You can get more details in Treadsoft Homepage
I hope this will help you.