Use the System File Checker tool to repair missing or corrupted system files

                           System File Checker is a utility in Windows that allows users to scan for corruptions in Windows system files and restore corrupted files. This article describes how to run the System File Checker tool (SFC.exe)  to scan your system files and to repair missing or corrupted system files in Windows 8.1, Windows 8, Windows 7 or Windows Vista. If a Windows Resource Protection (WRP) file is missing or is corrupted, Windows may not behave as expected. For example, some Windows functions may not work, or Windows may crash. 

Run the System File Checker tool (SFC.exe)

To do this, follow these steps:

1.Open an elevated command prompt. To do this, do the following as your appropriate

2.At the command prompt, type the following command, and then press ENTER:

sfc /scannow

 

 

                      The sfc /scannow command will scan all protected system files, and replace corrupted files with a cached copy that is located in a compressed folder at %WinDir%\System32\dllcache.
The %WinDir% placeholder represents the Windows operating system folder. For example, C:\Windows.

Note Do not close this Command Prompt window until the verification is 100% complete. The scan results will be shown after this process is finished.

3.After the process is finished, you may receive one of the following messages:

• Windows Resource Protection did not find any integrity violations.
  
  This means that you do not have any missing or corrupted system files.
• Windows Resource Protection could not perform the requested operation.
  
  To resolve this problem, perform the System File Checker scan in safe mode(ie. boot to safe mode ), and make sure that the PendingDeletes and PendingRenames folders exist under %WinDir%\WinSxS\Temp.
• Windows Resource Protection found corrupt files and successfully repaired them. Details are included in the CBS.Log %WinDir%\Logs\CBS\CBS.log.
  
  To view the detail information about the system file scan and restoration, go to How to view details of the System File Checker process.
• Windows Resource Protection found corrupt files but was unable to fix some of them. Details are included in the CBS.Log %WinDir%\Logs\CBS\CBS.log.
   
  To repair the corrupted files manually, view details of the System File Checker process to find the corrupted file, and then manually replace the corrupted file with a known good copy of the file.