How to Use SFC /Scannow to Repair Windows System Files – Next Century

The sfc scannow option is used to run System File Checker of your computer.

Sfc /scannow will inspect all of the important Windows files on your computer, including Windows DLL files.

If System File Checker finds an issue with any of these protected files, it will replace it.

1. Click on Start and type in CMD in the Type here to search box

NOTE: If you the Type here to search box is not visible, just start typing after you click start and it will appear

2. Right click on Command Prompt and select Run as administrator which runs an elevated Command Prompt

NOTE: For the sfc /scannow command to work properly, it must be executed from an elevated Command Prompt window in Windows 10, Windows 8, Windows 7 and Windows Vista. This is not required in previous versions of Windows.

3. Once Command Prompt is open, type the following command and then press Enter

sfc /scannow

NOTE: There’s a space between sfc and /scannow. Executing the sfc command with its option next to it (without a space) will result in an error

4. System File Checker will now verify the integrity of every protected operating system file on your computer which could take quite a while to finish.

Once “verification” reaches 100%, you’ll see something like this in the Command Prompt window, assuming issues were found and corrected:

  Windows Resource Protection found corrupt files and successfully repaired them.
  Details are included in the CBS.Log windir\Logs\CBS\CBS.log. 
  For example C:\Windows\Logs\CBS\CBS.log.
  Note that logging is currently not supported in offline servicing scenarios.

or something like this if no issues were found, you will get this message

  Windows Resource Protection did not find any integrity violations.

5. Restart your computer even if sfc /scannow did actually repair any files

How to Interpret the CBS.log File

Every time you run System File Checker, a LOG file is created that contains an itemized list of every file that was checked and every repair operating that took place if any.

Assuming Windows is installed on the C: drive (it usually is) then the log file can be found at C:\Windows\Logs\CBS\CBS.log. This file could be useful for advanced troubleshooting or as a resource for a tech support person that might be helping you out.

See Microsoft’s How to Analyze the Log File Entries Created by SFC article if you’re interested in diving into this file yourself.