1. A method comprising: providing an executable environment for application programs to be installed and executed with a peripheral storage device, the executable environment configured for execution within an operating system environment of a host system; providing an application for execution with the peripheral storage device, the application originally configured for fixed system installation and execution within the operating system environment of the host system, other than being portable from one such host system to another; installing the application within the executable environment, wherein files and data analogous to system related files and data of the application originally configured to be stored within the operating system environment of the host system are stored within the peripheral storage device; and executing the application within the executable environment, the executable environment intercepting a call made by the application for the host system to perform a function, and further: making an executable environment call to perform the function within the executable environment, if the intercepted call is supported therein; and making a system library call to the host system to perform the function, if the intercepted call is not supported by the executable environment and the intercepted call is supported by the host system.