sfc.exe

System Integrity Check and Repair (System file checker).

sfc.exe scans protected (system?) files to verify their versions. Corrupted (or otherwise overwritten files) versions are replaced with the correct version from the cache folder %SystemRoot%\System32\DllCache.

sfc.exe is typically used with the /scannow option:

C:\> sfc /scannow

sfc.exe needs Administrator privileges (eleveted prompt?) to be run.