I outlined in an earlier post how XP Mode gives Windows 7 users a very easy way to try out beta software without worrying that the main operating system install might be messed up.

Here is a screenshot of VS 2010 Beta 2 running on my Win7 desktop.  Notice that the only way to tell is that it has the blue Windows XP bar at the top instead of the Win 7 Aero bar like Task Manager in front of it.