Hi there! You haven’t mentioned which OS you are running on your desktop. Windows Server 2003 Datacenter Edition with Volume License capability allow running unlimited virtual machines hosting any flavor of Windows Server, Enteprise or Datacenter editions. Apart from this, VMWare offers a product called Virtual Desktop Manager or VDM (VMware View 3.x) that offers such capabilities.
However, both are costly solutions and typically used in enterprise environment.
Consider Solaris 10 on intel platform if you require a free solution. It offers built in zoning capabilities.
All said and done, virtualization on a desktop is not the best idea in terms of cost, complexity, implementation time. These are resource hungry applications and designed to run on enterprise class server hardware.