How to Check File integrity and Repair windows system flies.

What Is SFC /Scannow?

The sfc /scannow command is one of the several specific switches available in the sfc command, the Command Prompt utility invoking System File Checker.

While there are plenty of different things you can do with the command, sfc /scannow is the most common way that the sfc command is used.

Sfc /scannow will inspect all of the important Windows files on your computer, including Windows DLL files. If System File Checker finds a problem with any of these protected files, it will replace it.

How to Use SFC /Scannow

Follow these steps to repair Windows system files with sfc /scannow:

1. Open Command Prompt as an administrator, very often referred to as an “elevated” Command Prompt.For the sfc /scannow command to work properly, it must be executed from an elevated Command Prompt window.
2. Type the following command and then press Enter. “sfc /scannow” To use System File Checker from the Command Prompt through Advanced Startup Options or System Recovery Options, see the Executing SFC /SCANNOW From Outside of Windows section below for some necessary changes in how you execute the command.System File Checker will now verify the integrity of every protected operating system file on your computer. It might take a while to finish.

Run DISM Command If SFC Cannot Repair Corrupted Files

System File Checker is a utility built into the Operating System that will check for system file corruption The sfc /scannow command scans the integrity of all protected operating system files and replaces incorrect, corrupted, changed, or damaged versions with the correct versions where possible. When this command cannot repair the damage DISM should be run to fix as many errors as possible.

Step 1. Press Win + R to open Run dialog and type: cmd to open “Command Prompt”.

Step 2. Type the following command and hit “Enter”.

• To check the health：

Dism /Online /Cleanup-Image /CheckHealth

• To scan the health：

Dism /Online /Cleanup-Image /ScanHealth

• To restore the health：

Dism /Online /Cleanup-Image /RestoreHealth 

Step 3. Reboot PC to keep all changes and make SFC into working again.

After running DISM, you can re-run SFC just to check.

Conclusion

The System File Checker is a convenient tool to check whether there is a corruption for system files. However, if it is not working, you may receive an error message Windows resource protection could not perform the requested operation. But you can fix the error with these solutions above.

Credit: https://www.easeus.com/partition-manager-software/sfc-scannow-finds-corrupted-files-but-unable-to-fix.html
https://www.lifewire.com/how-to-use-sfc-scannow-to-repair-windows-system-files-2626161