Microsoft presented some info about a shadow copy feature in Windows Vista which they copied from Windows Server 2003.
The system automatically makes shadow copies of files and folders daily. You can also create shadow copies by setting a System Protection Point using the System Protection tab in the System control panel. When you right-click a file or folder, you now see a Previous Versions tab that lets you copy any of the stored previous versions or restore the item to any of the prior states.
In the event of an inadvertent change or deletion of a file or folder, Previous Versions allows you to revert the file or folder to any previous version, restore a previous version from a backup (made with Windows Backup), or make a copy of a previous version.