This is pretty cool:

a VPC virtual machine image containing a pre-activated Windows XP SP2, IE6 and the IE7 Readiness Toolkit to help facilitate your testing and development. The image is time bombed and will no longer function after April 1, 2007

http://blogs.msdn.com/ie/archive/2006/11/30/ie6-and-ie7-running-on-a-single-machine.aspx