Microsoft released a Virtual PC Image a while back which had Internet Explorer 6 installed on it. This was required because
you can’t successfully (I have tried) run both IE7 and IE6 on a Windows PC at the same time. Microsoft put a time limit on the
Virtual PC image so that there wouldn’t be copies of Windows floating around that anybody could use without a license.
The expiry date for the original image was April 1 so they have now released a new Virtual PC image with an expiry date of July 23rd.
This allows web developers to test their apps with both browsers succesfully during testing.

From IEBlog:

IEBlog : IE6 VPC Refresh Now Available
IE6 VPC Refresh Now Available

In my original blog post about releasing the IE6 Virtual PC Image, we mentioned that it would expire on April 1st, 2007 (no, it wasn’t an April Fool’s joke), and that we’d be releasing a new VPC image to replace it sometime in March. Well, I’m happy to report that I propped the new VHD up on Monday morning. You can download the image here. Take note that a free download of Virtual PC 2007 is now available, replacing VPC2004.

I didn’t make any major changes to the image other than adding the latest security updates. I also managed to reduce the download size to just under 400 megs, shaving off almost 100 megs from the previous image size. This image is time-bombed to July 23rd , but we will continue to release these images as long as they are needed. They are time-bombed because you get them for free. If you want images without time-bombs, an MSDN subscription is the way to go.