Microsoft released Internet Explorer 7 a few months ago, with some great features such as an RSS reader and tabs (my favorite). You, however, cannot run both Internet Explorer 6 AND Internet Explorer 7 on the same Windows installation. So if you are a web developer, and have to test your web pages in different versions of the browser, what can you do? Well, for one, you can thank Microsoft for releasing Virtual PC 2004 as a free download.
One of the known advantages of virtualization is the fact that you can run different configurations on the same machine. Microsoft is right now using this to help developers, by releasing AS A FREE DOWNLOAD a Virtual Machine image that contains a pre-activated Windows XP SP2 installation, Internet Explorer 6 and the IE7 Readiness Toolkit. With this VPC Image, you can run IE7 as the standard browser in your PC, and have and Virtual PC 2004 image with IE6 for testing purposes.
You can get more information about the VPC image in this post at the IEBlog. One of the downsides of the image, though, is that it has a "timebomb" and expires in April, 2007. But, between now and then, looks like the best alternative for running both browsers on your PC.
You can get the image from the Internet Explorer 6 Testing VPC Image download page