Earlier this week, Microsoft announced that Virtual PC is now available free of charge.
Whether Microsoft virtualization technology is an important component of your existing infrastructure or you're just a Virtual PC enthusiast, you can now download Virtual PC 2004 absolutely free. Microsoft is also offering the free download of Virtual PC 2007, with support for Windows Vista in 2007.
You may recall in April that Microsoft made Virtual Server available free of charge (Free Download: Virtual Server 2005 R2).
Virtual PC or Virtual Server can be your best friend when wanting to install CTP releases on your best hardware without interfering with your day job applications and OS.