On a Linux server, you have both built-in virtualization options as well as third-party free and commercial options. While you can easily create a virtual server that runs Linux, only some virtualization software lets you create virtual servers for Windows Server 2008 or other Windows server versions.
KVM – This virtualization tool is a standard Linux feature called kernel-based virtual machine. You can use it to create virtual servers for x86 operating systems on hardware with virtualization extensions (Intel VT or AMD-V). KVM supports both Linux and Windows images.
Xen hypervisor supports Linux, Windows, Solaris, BSD, and other operating systems. Like KVM it requires virtualization extensions.
VirtualBox Headless – Oracle’s VirtualBox uses a graphical interface by default, but you can use the headless feature to run it on a server. VirtualBox supports various versions of Windows, as well as many other operating systems.
VMWare also offers many commercial options for virtualization, among which is the ability to run Windows server virtual machines within Linux.
Virtualization uses a very thin layer between the hardware and the virtual machine, making it much faster than hardware emulation. This means that you can get near-native performance out of your virtual machines, even with Windows running on a Linux server.