System Restore

System Restore

System Restore in Windows 7
Developer(s)	Microsoft
Initial release	Windows Me / 4.90.3000 / June 19, 2000
Stable release	Windows 7 / 6.1.7600.16385 / July 22, 2009
Operating system	Microsoft Windows
Type	System administration
License	Microsoft EULA

System Restore is a component of Microsoft's Windows Me, Windows XP, Windows Vista and Windows 7, but not Windows 2000,^[1] operating systems that allows for the rolling back of system files, registry keys, installed programs, etc., to a previous state in the event of system malfunction or failure.

The Windows Server operating system family does not include System Restore. The System Restore built into Windows XP can be installed on a Windows Server 2003 machine,^[2] although this is not supported by Microsoft.

In Windows Vista and later versions, System Restore has an improved interface and is based on Shadow Copy technology. In prior Windows versions it was based on a file filter that watched changes for a certain set of file extensions, and then copied files before they were overwritten.^[3] Shadow Copy has the advantage that block-level changes in files located in any directory on the volume can be monitored and backed up regardless of their location.^[4]

Overview

In System Restore, the user may create a new restore point manually, roll back to an existing restore point, or change the System Restore configuration. Moreover, the restore itself can be undone. Old restore points are discarded in order to keep the volume's usage within the specified amount. For many users, this can provide restore points covering the past several weeks. Users concerned with performance or space usage may also opt to disable System Restore entirely. Files stored on volumes not monitored by System Restore are never backed up or restored.

System Restore backs up system files of certain extensions (.exe, .dll, etc.) and saves them for later recovery and use.^[5] It also backs up the registry and most drivers.

Resources monitored

The following resources are backed up:^[6]

• Registry
• Files in the Windows File Protection (Dllcache) folder
• Local user profile
• COM+ and WMI Databases
• IIS Metabase
• Specific file types monitored ^[5]

The list of file types and directories to be included or excluded from monitoring by System Restore can be customized on Windows Me and Windows XP by editing %windir%\system32\restore\Filelist.xml.^[7]

Restore points

Restore points are created:

• When software is installed using the Windows Installer, Package Installer or other installers which are aware of System Restore.^[8]
• When Windows Update installs new updates to Windows.
• When the user installs a driver that is not digitally signed by Windows Hardware Quality Labs.
• Every 24 hours of computer use^[8] (10 hours in Windows Me), or every 24 hours of calendar time, whichever happens first. This setting is configurable through the registry or using the deployment tools. Such a restore point is known as a system checkpoint. System Restore requires Task Scheduler to create system checkpoints. Moreover, system checkpoints are only created if the system is idle for a certain amount of time.^[6]
• When the operating system starts after being off for more than 24 hours.
• When the user requests it. On Windows Vista, shadow copies created during File Backup and Complete PC Backup can also be used as restore points.^[4]

In Windows XP, restore point files are stored in a hidden folder named System Volume Information on the root of every drive, partition or volume, including most external drives, and some USB flash drives. On drives or partitions that are not monitored by System Restore this folder will be very small in size or completely empty, unless Encrypting File System is in use or the Indexing Service is turned on. Note: If the System Volume Information folder is deleted, it will be recreated automatically.

Older restore points are deleted as per the configured space constraint on a First In, First Out basis.

Implementation

There are considerable differences between how System Restore works under Windows XP and Windows Vista.

• Maximum space - In Windows XP, System Restore can be configured to use up to a maximum of 12% of the volume's space for most disk sizes;^[6] however, this may be less depending on the volume's size. Restore points over 90 days old are automatically deleted, as specified by the registry value RPLifeInterval (Time to Live - TTL) default value of 7776000 seconds.
  In Windows Vista, System Restore is designed for larger volumes and cannot be enabled on volumes smaller than 1 GB.^[9] By default, it uses 15% of the volume's space.^[8] Using the command-line tool Vssadmin.exe or by editing the appropriate registry key,^[10][11] the space reserved can be adjusted.

• File types - Up to Windows XP, files are backed up only from certain directories.
  On Windows Vista, this set of files is defined by monitored extensions outside of the Windows folder, and everything under the Windows folder.^[12]

• My documents folder - Up to Windows XP, it excludes any file types used for users' personal data files, such as documents, digital photographs, media files, e-mail, etc. It also excludes the monitored set of file types (.DLL, .EXE etc.) from folders such as My Documents. Microsoft recommends that if a user is unsure as to whether certain files will be modified by a rollback, they should keep those files under My Documents.^[6] When a rollback is performed, the files that were being monitored by System Restore are restored and newly created folders are removed.
  However, on Windows Vista, it excludes only document file types; it does not exclude any monitored file type whatsoever its location and operates on the entire volume.

In Windows XP only, several System Restore settings can be configured via the Registry.^[13]

Restoring the system

Up to Windows XP, the system can be restored as long as Windows boots normally or from Safe mode. It is not possible to restore the system if Windows is unbootable. Under Windows Vista, the Windows Recovery Environment can be used to launch System Restore and restore the system, in case the Windows installation is unbootable.^[4] For all operating systems including Windows XP, the Diagnostics and Recovery Toolset (DaRT) tools from the Microsoft Desktop Optimization Pack can be used to create a bootable recovery disc that can log on to the unbootable Windows installation and start System Restore.

Limitations & complications

This article may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (May 2008)

A limitation which applies to System Restore in Windows versions prior to Windows Vista is that only certain file types and files in certain locations on the volume are monitored, therefore unwanted software installations and especially in-place software upgrades may be incompletely reverted by System Restore.^[14] Consequently, there may be little or no practical beneficial impact. Certain issues may also arise when attempting to run or remove that application. In contrast, various other utilities have been designed to provide much more complete reversal of system changes including software upgrades. For example, by tracking all changes, Norton's GoBack or Horizon DataSys's RollBack Rx allows complete restoration of the file system's state to any of hundreds of available restore points per day. Another example would be Faronics Deep Freeze which restores the entire disk volume to its original configuration upon restart, eradicating unwanted changes of any type.^[15] Frequent or continuous monitoring may also adversely affect system performance, whereas System Restore's restore points are generally created quickly and sparingly.^{[original research?]}

If there is no adequate free space, System Restore will fail to create a restore point. In this case, the user may discover that there is not a single restore point available with which to restore the system.

It is not possible to create a permanent restore point. All restore points will eventually be deleted after the time specified in the RPLifeInterval registry setting is reached or earlier if allotted disk space is insufficient. Even if no user or software triggered restore points are generated allotted disk space is consumed by automatic restore points.^[6] Consequently, in systems with little space allocated, if a user does not notice a new problem within a few days, it may be too late to restore to a configuration from before the problem arose.

In Windows Me and FAT32 drives, for data integrity purposes, System Restore does not allow other applications or users to modify or delete files in the directory where the restore points are saved. Since its method of backup is fairly simplistic, it may end up archiving malware such as viruses, for example in a restore point created before using antivirus software to clean an infection. Antivirus software is usually unable to remove infected files from System Restore;^[16] the only way actually to delete the infected files is to disable System Restore, which will result in losing all saved restore points; otherwise they will remain until Windows deletes the affected restore points. However stored infected files in themselves are harmless unless executed; they will only pose a threat if the affected restore point is reinstated.

In Windows XP and after using NTFS drives, System or Administrator rights are required to modify or delete files in the restore point folders.

On Windows Vista, System Restore does not work on FAT32 disks and cannot be enabled on disks smaller than 1 GB.^[9]

Changes made to a volume from another OS (in case of dual-boot OS scenarios) cannot be monitored. Also, a compatibility issue exists with System Restore when dual-booting Windows XP/Windows Server 2003 and Windows Vista or later operating systems. Specifically, the shadow copies on the volume are deleted when the older operating system accesses (and therefore mounts) that NTFS volume. This happens because the older operating system does not recognize the newer format of persistent shadow copies.^[17]

System Restore in Windows Vista and later versions no longer supports configuring its settings through the registry.^[18] File types and directories can also no longer be included or excluded from monitoring by System Restore by editing %windir%\system32\restore\Filelist.xml as was possible in Windows XP. This file no longer exists in Windows Vista.^[7]

See also

• Backup
• Time Machine

References

External links

• Important update that fixes a problem with Windows Me's version of System Restore when restoring a checkpoint after September 8, 2001.
• System Restore: Limitations and Complications
• Microsoft article KB295659