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Description of Windows XP and Windows Server 2003 System File Checker (Sfc.exe)

Support for Windows XP has ended

Microsoft ended support for Windows XP on April 8, 2014. This change has affected your software updates and security options. Learn what this means for you and how to stay protected.

Support for Windows Server 2003 ended on July 14, 2015

Microsoft ended support for Windows Server 2003 on July 14, 2015. This change has affected your software updates and security options. Learn what this means for you and how to stay protected.

This article was previously published under Q310747
For a Microsoft Windows 2000 version of this article, see 222471.
Summary
This article describes System File Checker (Sfc.exe), which is a command-line utility used with the Windows File Protection (WFP) feature.
More information
System File Checker gives an administrator the ability to scan all protected files to verify their versions. If System File Checker discovers that a protected file has been overwritten, it retrieves the correct version of the file from the cache folder (%Systemroot%\System32\Dllcache) or the Windows installation source files, and then replaces the incorrect file. System File Checker also checks and repopulates the cache folder. You must be logged on as an administrator or as a member of the Administrators group to run System File Checker. If the cache folder becomes damaged or unusable, you can use the sfc /scannow, the sfc /scanonce, or the sfc /scanboot commands to repair its contents.

System File Checker Tool Syntax

Sfc [/Scannow] [/Scanonce] [/Scanboot] [/Revert] [/Purgecache] [/Cachesize=x]
  • /Scannow: Scans all protected system files immediately and replaces incorrect versions with correct Microsoft versions. This command may require access to the Windows installation source files.
  • /Scanonce: Scans all protected system files one time when you restart your computer. This command may require access to the Windows installation source files when you restart the computer. The SfcScan DWORD value is set to 2 in the following registry key when you run this command:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
  • /Scanboot: Scans all protected system files every time you start your computer. This command may require access to the Windows installation source files every time you start your computer. The SfcScan DWORD value is set to 1 in the following registry key when you run this command:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
  • /Revert: Returns scan to the default setting (do not scan protected files when you start the computer).The default cache size is not reset when you run this command. This command is equivalent to the /Enable switch in Windows 2000.
  • /Purgecache: Purges the file cache and scans all protected system files immediately. This command may require access to the Windows installation source files.
  • /Cachesize=x: Sets the file cache size to x megabytes (MB). The default size of the cache is 50 MB. This command requires you to restart the computer, and then run the /purgecache command to adjust the size of the on-disk cache. This command sets the SfcQuota DWORD value to x in the following registry key:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
For additional information about the Windows File Protection feature, click the article number below to view the article in the Microsoft Knowledge Base:
222193 Description of the Windows 2000 Windows File Protection Feature
compatguidechange wfp sfp switches tool
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Article ID: 310747 - Last Review: 05/22/2013 15:28:00 - Revision: 5.0

Microsoft Windows Server 2003, Enterprise x64 Edition, Microsoft Windows Server 2003, Datacenter Edition (32-bit x86), Microsoft Windows Server 2003, Enterprise Edition (32-bit x86), Microsoft Windows Server 2003, Standard Edition (32-bit x86), Microsoft Windows Server 2003, Web Edition, Microsoft Windows XP Home Edition, Microsoft Windows XP Professional, Microsoft Windows XP Professional x64 Edition, Microsoft Windows XP Media Center Edition 2005 Update Rollup 2, Microsoft Windows XP Tablet PC Edition

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