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, wherein said creating of said long-term snapshots from time-to-time comprises creating said long-term snapshots prior to significant adjustments during said migration process.