Here are the Windows 2008 license requirements for running vms in any virtual environment. Licensing Microsoft Windows Server 2008 to Run with Virtualization Technologies VMware’s ESX Server, VMware’s VMotion, Microsoft’s System Center Virtualization Machine Manager, and Parallels’ Virtuozzo.
Windows Server Licensing on top of VMware’s ESX
If a server is running ESX as the virtualization technology, then Windows Server is not deployed as a host operating system in the physical OSE. However, a license is required for every instance running in a virtual OSE.
If you have assigned a single license for Windows Server 2008 Standard to a server running ESX, then you may run one instance of Windows Server 2008 Standard at a time. The right to run an instance of Windows Server 2008 in the physical OSE cannot be used in this case since ESX runs on the physical OSE (and as a result, Windows Server 2008 cannot be deployed as the operating system on the physical OSE.)
If you have assigned a single license of Windows Server 2008 Enterprise to the server running ESX, then you may run up to four instances at a time of Windows Server 2008 Enterprise. You may not run a fifth instance under the same license since that right requires that the fifth instance be running hardware virtualization software and software managing and servicing the OSEs on the server.
