It's worth noting that host-based (like VMWare workstation, virtual box, etc.) virtual machines are *much* slower (per clock cycle) and have a far higher overhead than hypervisor-based (VMWare ESX, Hyper-V, Xen, etc) virtual machines. However, if you install hypervisor-based virtual machine software (like hyper-v), you lose all ability to put the machine to sleep or hibernate while the hypervisor is enabled. This is one of the main reasons to still consider host-based virtual machine software on a server OS when running on a desktop or laptop. However, if you're installing server on a machine that will run like a server (on 24/7 while someone is using it), it would be far better to use the hypervisor-based software to run VMs if performance is a concern or issue.