Shadow Copy
This feature is included in the following editions of Windows Vista:
Available in the Ultimate, Business, and Enterprise editions of Windows Vista, this feature creates point-in-time copies of files as you work, so you can retrieve versions of a document you may have accidentally deleted. Shadow copy is automatically turned on in Windows Vista and creates copies on a scheduled basis of files that have changed. Since only incremental changes are saved, minimal disk space is used for shadow copies.
Access this feature by right-clicking a file or folder and selecting "Restore previous versions." It enables you to go back in time and access your files and folders as they were on previous dates. You can preview each file in a read-only version to determine which file to restore. Then, to fully restore it, you can just drag the file to a folder, or select it and click "Restore" to restore it to its original location.
Shadow Copy helps you recover a file if you accidentally delete it.
It works on single files as well as whole folders. When restoring a file, all previous versions that are different from the live copy on the disk are shown. When accessing a previous version of a folder, users can browse the folder hierarchy as it was in a previous point in time.