I found this link, which is great for latest releases, but, I need to find older versions as well: http://capitalhead.com/articles/how-to-find-build-and-revision-number-of-windows-vista-or-windows-server-2008-installed.aspx

http://en.wikipedia.org/wiki/List_of_Microsoft_Windows_versions That is a good start, I would also look at the support lifcycle of the products: http://support.microsoft.com/lifecycle/search/default.aspx?alpha=Windows+XP That can help you make the case of not going through the cost and expenses of maintaining no supported products.-- :P Advice offered, If you need more help it is advised to seek the council and advice of paid professionals. The answer is always 42, or reboot.