For web designer and web developer must havo to running and testing the web page in all the most populars browsers.
The most populars browsers are Internet Explorer and Firefox (then Safari for Mac users). But for the Microsoft browser, there are a lot of differences between version 6 and 7.
Then is indispensable to have installed both versions.

Ufficially is not possible. But ther is a program, a Virtual Machine, that can do this!

The first step is to install the Explorer 7.0 version with his standard setup. Than you must download Multiple IE Emulator. After the installation of this program, you are able to execute in standalone mode all the Explorer version you want (more or less :-))! From the third release to the 6th.

But we know there are some problems for the versions 3+ in Windows Vista…