From HowToGeek

Volume Snapshot Service (VSS) is a feature that allows taking a "snapshot" of a file or folder on a volume. This is used in Windows Vista to power the Previous Versions and System Restore features, but it's also used in all versions of Windows to allow backing up of files even though they are in use.

Contents 1 Overview 2 History 3 Dual Booting Issues 4 See Also 5 References

Overview

The snapshot service creates a read-only "snapshot" of the volume, and allows applications to access that snapshot without having to deal with any file locking issues.

History

This feature was added in Windows XP as of Service Pack 1. Originally, only temporary snapshots could be created for the purposes of backups.

With Windows Server 2003, the ability to allow persistent snapshots was created, with the name Shadow Copies for Shared Folders.

Windows Vista added the ability to save shadow copies for all users, but only Vista Business or Ultimate users can access those files via the Previous Versions interface.

Dual Booting Issues

If you dual-boot with Windows XP, it will destroy the shadow copies created by Windows Vista. You'll need to use a registry hack to prevent XP from being able to see the Vista drive.

See Also

• System Restore
• Previous Versions

References

Backup or Copy Files that are In Use or Locked

List of Windows Components v
Features	Windows Aero - System Restore - Previous Versions - SuperFetch - User Account Control (UAC) - Offline Files - ReadyDrive - Instant Search - Windows Sidebar - Parental Controls - Speech Recognition - ClearType - DirectX 10 - ReadyBoost - BitLocker - Flip3D - Remote Desktop - Search Folders - Tablet PC - Windows SideShow
Services	Task Scheduler - Desktop Window Manager - Application Experience - Application Host Helper Service - Application Information - Application Layer Gateway Service - Application Management - Background Intelligent Transfer Service - Base Filtering Engine - Block Level Backup Engine Service - Certificate Propagation - COM+ Event System - Computer Browser - DHCPClient
Applications	Notepad - Windows Mail - Internet Explorer - Command Prompt (Cmd.exe) - Windows Calendar - Mobility Center - Task Manager - Photo Gallery - Windows Media Center - Windows Media Player - Wordpad - Windows Sidebar - Snipping Tool - Windows Contacts - Device Manager - Disk Defragmenter - Event Viewer - Fax and Scan - Windows Journal - Windows Meeting Space - Windows DVD Maker - Windows Easy Transfer
Security	User Account Control (UAC) - Windows Defender - Windows Firewall
Admin Tools	Control Panel - Device Manager - Microsoft Management Console (MMC)