System File Checker For Windows XP

Recently on the forums we have had some interest in the SFC in Windows
XP. This brief tutorial shows Windows XP Administrators how to use SFC
for Windows XP.

Level: EASY

Scans and verifies the versions of all protected system files after you restart your computer.


sfc [/scannow] [/scanonce] [/scanboot] [/revert] [/purgecache] [/cachesize=x]


/scannow: Scans all protected system files immediately.
/scanonce: Scans all protected system files once.
/scanboot: Scans all protected system files every time the computer is restarted.
/revert: Returns the scan to its default operation.
/purgecache: Purges the Windows File Protection file cache and scans all protected system files immediately.
/cachesize=x: Sets the size, in MB, of the Windows File Protection file cache.
/?: Displays help at the command prompt.


  • You must be logged on as a member of the Administrators group to run sfc.
  • If sfc discovers that a protected file has been overwritten, it
    retrieves the correct version of the file from the
    %systemroot%system32dllcache folder, and then replaces the incorrect
  • If the %systemroot%system32dllcache folder becomes corrupt or
    unusable, use sfc /scannow, sfc /scanonce, or sfc /scanboot to repair
    the contents of the Dllcache directory.

Please note that this Command Line reference is to

the integrity
of the Windows XP DLL’s that were shipped with Windows XP. It will try
to repair damaged DLL’s by prompting for the Windows CD.

The Windows XP System File Protection which remains active in the
background monitors these DLL’s and if it detects an altered DLL, it will
alert a user with a popup message asking for the Windows XP CD. This is
so that it can

the corrupt DLL back to its original state.

SFC checker in Windows XP can only be

run by an Administrator and is
not ran in the same way as its previous incarnation from the Windows 98


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