Volume Shadow Copy Technology
Arstechnica provides details on Microsoft's attempt to provide support for previous versions.
Microsoft recently revealed that Windows Vista would inherit "volume
shadow copy" technology from Windows XP and Windows Server 2003. In
those older operating systems, volume shadow copy is used to take
periodic snapshots of key system files, though the service can also be
instructed to monitor any kind of data for the purposes of creating a
system "restore point."