You can run the System File Checker to verify protected system files.

Command line switches are:

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.