System File checker is that utility which checks system files and looks for corruptions or violations of integrity in the files and restores them accordingly. System File checker was available in the predecessors of Windows 7, 8 and Vista but what’s new with the SFC of these 3 versions is that the SFC is blended with Windows Resource Protection (WRP). So SFC together with WRP provides security to critical system files, registry keys and folders.
Windows Resource Protection notifies for any changes in the system files or registers in Winlogon. If a violation of integrity is encountered, the modified file is restored from a cached copy which is located in a folder at %WinDir%\System32\dllcache. So when sfc/scannow command is run at boot or command, the Windows Resource Protection starts verifying the important files, and at the end if the WRP does not find any corruption, it will show the message Windows Resource Protection did not find any integrity violations. One thing that must be remembered that the scanning should be performed through elevated Command Prompt.
Steps to Run the “SFC /SCANNOW” Command at Boot or in Windows 8
1. Press Windows + X and a list of functions will appear. Select the Command Prompt (Admin). If prompted by UAC, click Yes to confirm. This opens the Elevated Command Prompt.
2. Type the following command sfc/scannow and press Enter.
3. Verification will start. the process is a little time consuming.
4. When verification process is complete, the message Windows Resource Protection did not find any integrity violations will be displayed if the integrity is not violated.