1. A non-transitory computer readable medium comprising computer executable instructions which when executed by a computer cause the computer to perform the method of: during a process of migrating a source system into a standardized virtual environment, snapshotting virtual machine instances of said source system executing in a hypervisor as virtual machine images in an operational repository of said hypervisor, said virtual machine images in said operational repository comprising short-term snapshots; and from time to time during said migration process, creating long-term snapshots of said source system by checking given ones of said virtual machine images from said hypervisor operational repository into an image library as image objects.