It’s well known that, with a Windows Server 2008 R2 installation, you can simply add the Hyper-V role to your server, as long as your hardware supports the role.  Once the Hyper-V role is added, you can host virtual machines n the server.  However, you still have the full installation of Windows running from which you launched the role addition.  This is overhead.

You can install the free Microsoft Hyper-V Server 2008 R2 product right onto the bare metal without the full Windows overhead.  That said, going this route will require that you either manage Hyper-V from the command line or from a computer that has full installation of Windows Server 2008 R2 or Windows 7.  This will allow you to run the GUI-based Hyper-V Manager so that you don’t have to deal with the command line.