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

 sfc /scannow

The sfc util­i­ty will run for a while and if any cor­rup­tions are found, replace them on re-boot.

sfc switch­es:

Scan once at next boot:   sfc /scanonce
Scan at every boot:  sfc /scanboot
Purge File Cache:  sfc /purgecache
Return to Default Setting:  sfc /revert

SOURCE:
http://www.thewindowsclub.com