Riddle me this: How many licenses of Windows Server Enterprise Edition would you need if you are planning on running 20 Virtual machines inside a server that has 2 processors? Very, easy, you would need only 5 licenses. Too tough? How about this one...what would be the price difference if you were running 50 machines running Windows Server 2003 on a virtualization server with 2 processors if you chose to run the host machine with Windows Server Enterprise Edition vs. Windows Server Datacenter Edition? Very easy...running Datacenter edition would be $25,580 cheaper.
It definitely is tempting to say that I can pull this info right off the top of my head, but that would be a big big lie. The secret lies in the sweet web application Microsoft has published. It is called the
Windows Server Virtualization Calculator, and without a doubt, it will clear a lot of doubts and will show you the best way to go (in terms of licensing) when consolidating your data center, enjoy!