Abstract: This invention relates to virtualised systems, in particular to portable virtualised systems whereby a user is able to transfer their desktop environment from one computing machine to another. A method of providing a transferable computing environment between a computing machine and a portable storage device is described whereby the operational state of the computing environment is maintained after the transfer. A virtual machine is portioned into a common portion and a second portion, the second portion storing a state of operation of the virtual machine and the state of applications. The second portion is transferred to a computing machine to be used in combination with the common portion of the virtual machine already residing on the computing machine.