Abstract: A sequence of programs enable execution of a guest operating system (OS) (116) installed on virtual hard disks (VHDs), one storing system, one storing user data (210, 212). The VHDs are stored on a storage device as for example a USB flash drive (216). The storage device is connected to a host system (110). Virtual machine monitor (VMM) (118) type, available RAM and an access path to an internal storage device (220) are detected. The guest OS (116) configuration is modified to support hardware emulated by the detected VMM. A virtual machine (VM) configuration for this VMM is created allocating a portion of the detected RAM for the VM (112). Both VHDs are attached as copy-on-write VHDs, and VM write operations to VHDs (210, 212) are redirected to overlay files (228, 230) on the host's internal storage device. After shutdown overlay files can be merged with corresponding VHD base files.

Abstract: A set of programs enable the start and the efficient and secure operation of an operating system (OS) installed on a virtual hard disk that is stored on an external storage device. When the external storage device is connected to a host system, a user can start the OS in a virtual machine on the host system. The virtual machine execution is controlled by a virtual machine monitor (VMM) installed on the host system. At startup of the program, the type of VMM installed on the host system is autodetected. Host system parameters that are relevant for an optimal configuration of the virtual machine, such as the amount of available physical memory, are captured. Before launch of the virtual machine the OS installed on the virtual hard disk is dynamically modified to support hardware emulated by the selected VMM. Configuration templates and scripts for supported VMM types are stored on the external storage device.