1. A method for accessing, by application programs, resources provided by an operating system, the method comprising: (a) receiving, by a process executing in an isolation environment comprising an application isolation layer and a user isolation layer, a request for a resource and an identifier associated with the resource; (b) determining, by consulting a rules engine in which possible rules comprise the actions of redirect, ignore, and isolate, that the appropriate action is to redirect the request and identifier associated with the resource to a location outside the isolation environment; (c) redirecting the request for the resource and the identifier associated with the resource to the determined location; and (d) responding to the request for the resource using an instance of the resource residing in the determined location.