How to force windows file protection to check it's files

sfc /scannow

Help menu below, for reference.

#  sfc /?
Microsoft(R) Windows XP Windows File Checker Version 5.1
(C) 1999-2000 Microsoft Corp. All rights reserved

Scans all protected system files and replaces incorrect versions with correct Mi
crosoft versions.

SFC [/SCANNOW] [/SCANONCE] [/SCANBOOT] [/REVERT] [/PURGECACHE] [/CACHESIZE=x]

/SCANNOW        Scans all protected system files immediately.
/SCANONCE       Scans all protected system files once at the next boot.
/SCANBOOT       Scans all protected system files at every boot.
/REVERT         Return scan to default setting.
/PURGECACHE     Purges the file cache.
/CACHESIZE=x    Sets the file cache size.