In Windows 7 & Vista, the System File Checker is integrated with Windows Resource Protection, which protects registry keys and folders as well as critical system files. If any changes are detected to a protected system file, the modified file is restored from a cached copy located in the Windows folder itself.
Open cmd ( admin rights ) and run
The sfc utility will run for a while and if any corruptions are found, replace them on re-boot.
Scan once at next boot: sfc /scanonce Scan at every boot: sfc /scanboot Purge File Cache: sfc /purgecache Return to Default Setting: sfc /revert