http://blogs.technet.com/curiousgeorge/archive/2008/12/04/it-pro-top-faqs-october-08.aspxQ) How do I downgrade? A) As an end user you have the right to downgrade as set out in your Software Licence Terms. Example: You’re buying a new computer system and it needs to run the same operating system as your existing 10 systems — Windows XP Professional.en-USCommunityServer 2.1 SP1 (Build: 61025.2)