Perhaps you have heard of this or maybe not, but one of the innovative features of Vista is its Shadow Copy feature, which is something previously introduced with Windows Server 2003. It is essentially a background copy operation that is performed by the system in order to make previous versions of a file available via the file/folder properties dialog. By creating these point-in-time copies of files as you work, you gain the benefit of being able to easily retrieve versions of a document that has been deleted or otherwise corrupted.

Shadow copies are automatically saved as part of a restore point. When System Protection is turned on (it is by default), Windows automatically creates shadow copies of any files that have been changed since the time the last restore point was made. Restore points are created once per day and before significant system events such as program or driver installation (and you can trigger one manually from the System Protection area of the System Properties control panel applet).