Don't have an extra machine handy to try that new beta product? IE7 on XP? Vista? Office 2007? Load it up in a Virtual PC! I've used Virtual PC for a long time now. I found it most useful in my Microsoft Consulting days as it made it easy for me to simulate server environments on my developer workstation.
Recently, I went through the exercises of installing Vista Beta 2 in a VPC. Thanks to the many great posts at the Virtual PC Guy and Virtually Vista blogs my experience was pretty smooth.
Keep these two blogs handy anytime you want to virtualize something using Virtual PC or Virtual Server (which, by the way, is now free!):
Virtual PC Guy: http://blogs.msdn.com/virtual_pc_guy/default.aspx
Virtually Vista: http://blogs.msdn.com/mikekol/
Note: Virtual PC Guy has several fun posts on loading up old and obsolete software, such as MS Bob, as well some really fun video games you might remember from back in the day.