Always thought this didn't make sense: Virtual Server is Free - but you have to buy Virtual PC. Finally we've fixed it - both products are now FREE. You can download your FREE copy of Virtual PC 2004 here: http://www.microsoft.com/windows/virtualpc/default.mspx
Microsoft will anounce changes to both Windows Server Data Center Edition and Virtualisation today at the World Wide Partner Conference in Boston.
Data Center will be available under Volume License agreements from 1st October. The Data Center Program will still exist (where you get to buy a solution with a Service Leval Agreement from our OEMs) but you'll also be able to get Data Center edition on any server (2 - 64 processors).
If you're running Data Center edition, you'll be free to run as many Windows Servers as you like as Virtual machines on that box.
I've no idea how much Data Center will cost, but it does appear to be a pretty appealing offering (no need to count licenses for your Virtual machines)...