With Microsoft, you would either use the free Microsoft Hyper-V Server or Windows Server 2008, the purchase the System Center suite (which includes Operations, Configuration, Data Protection, and Virtual Machine Manager). For VMware, you would buy Windows Server 2008 also (for the guest OS licenses) and then VI3 or vSphere Enterprise. If you include the cost of Windows, the VMware solution is 3 times the cost of Microsoft. If you do not need Windows (you already have licenses for Windows), then Vmware is 5 times more expensive.