1. A method for providing secure access to a plurality of secure networks from a single computing device, the method comprising: running on the computing device a virtual machine monitor, wherein the virtual machine isolates a plurality of commercial desktop operating systems, the desktop operating systems running within separate virtual machines on a host operating system, the host operating system comprising a commercial operating system; binding a physical network adaptor on the host to a virtual adaptor assigned to each virtual machine, wherein the physical network adaptor is connected to one of the secure networks: and assigning user security contexts on the host operating system to the virtual machines, wherein the user security contexts isolate the virtual machines as separate users on the host operating system through the use of discretionary access control lists.