A method and system that provides a pass through block device that is utilized to redirect all the writes bound to the system drive(s) to an overlay skin device. Reads are performed on overlay device contents and the overlay device contents take precedence over the contents of the base device. Applications of a particular theme may be installed on the overlay device. The overlay device is provided on a removable media and thus allows for creation of a set of exchangeable skins. Nested overlays are utilized to create separation of the OS data, application data, and user data. Switchable user skins enable writes into overlays and allow a user to create operating environments which can be utilized to change the use of a computer system. Since the overlays are provided on a removable media, the user only needs to substitute the overlay to switch the user's operating environment.