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 Service Pack 1 absolutely free. Microsoft is also offering the free download of Virtual PC 2007, with support for Windows Vista in 2007.
Virtual PC 2004 Service Pack 1 (SP1) is a powerful software virtualization solution that allows you to run multiple PC-based operating systems simultaneously on one workstation, providing a safety net to maintain compatibility with legacy applications while you migrate to a new operating system. It also saves reconfiguration time, so your support, development, and training staff can work more efficiently.
Download it here: http://www.microsoft.com/windows/virtualpc/default.mspx