An extensible virtualization system provides an object model and manages a virtual application lifecycle in a way that allows new virtualization subsystems to be added to extend a virtualization product without reworking the product itself. Virtualizing an application generally involves three steps: metadata extraction, metadata storage and reconstitution, and runtime management of requests. The extensible virtualization system receives notification of an application preparation session and allows virtualization subsystems to monitor the session to collect configuration information specific to each subsystem that the application uses to run on a client. Each subsystem provides collected information to the extensible virtualization system, which stores the collected information until the application to be virtualized is deployed. When the application is deployed, the system invokes the same virtualization subsystem and provides the subsystem with the stored information.