Windows Vista uses a service called Volume Shadow Copy Service which is turned on by default on all versions of Windows Vista. With the service turned on the Volume Shadow Copy Service creates so called shadow copies of files in Windows Vista from time to time which are ideal if you have to restore files [...]
Browse and Restore Shadow Copies in Windows Vista
Shadow Copies have been introduced into Windows XP Service Pack 1 and been extended in Windows Vista where it is used in System Restore and backup utility. You might have come upon the problem that a file was in use when trying to copy, move or delete it. Shadow Copies are used to copy every file, basically state of the art read only copies of files on the hard drive. This means that even important system files that are running all the time can be backed up without difficulties.
