There are times your Windows computer malfunctions, reporting errors about missing DLL or other types of files. The best way to handle this is to restore Windows corrupted files using the System File Checker (SFC) and its /scannowoption.

SFC is a utility in Windows that allows users to scan for corruptions in Windows system files and restore corrupted files. It scans and repairs missing or corrupted system files on your computer, allowing you to continue working properly.

One of the most useful commands in SFC is /scannow, which inspects all the important Windows files on your computer. If SFC finds an issue with any of these system files, it restores them back to normal.

Below you will find a thorough tutorial on how to restore Windows system files using the SFC /scannowoption. In addition, you will learn how to resolve common errors that may occur during the process, and how to run Offline SFC, and in Safe Mode.

Repair system files using SFC and /scannow

Microsoft created the System File Checker in order for users to easily repair their damaged system files. Someone might accidentally delete a DLL file, or a corruption in the system might damage it. But not beyond repair, since thanks to SFC with a simple procedure you can restore these system files.

What you need to do first, is to open Command Prompt as an administrator, also known as elevated Command Prompt.

In order to do that you will have to follow these steps:

  1. Open Task Manager: The quickest way is to hit Ctrl+Shift+Esc on your keyboard.
  2. Go to the File menu and click Run new task
  3. In the Create New Task window type cmd
  4. Check the box that says Create this task with administrative privileges
  5. Press OK

When the Command Prompt is open, you are ready to run SFC using its /scannow option.

To do so, type the following command in Command Prompt and press Enter:

sfc /scannow

 

The System File Checker will begin a verification procedure, scanning all your system files to detect corruptions or missing files.

SFC results and how to analyze the log file

Once the process of scanning for corrupted Windows system files is complete, System File Checker will create a report for you.  If SFC detected corrupted system files and restored them, you will see the following message in Command Prompt:

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.

In that case, a log file has been created for you to check and look for the repairs that SFC did. Microsoft provides a support blog which explains the process of analyzing the log file that SFC creates after scanning for corrupted or missing Windows system files.

If no issues were found, you will see the following message:

In case sfc /scannowrepaired any files, restart your computer. After your computer boots, repeat whatever process caused your original problem to make sure that sfc /scannowcorrected the issue. This process also works in Safe Mode.

How to use Offline System File Checker

If you are still a Windows XP user, you can use the command sfc /scanbootto tell Windows scan all protected system files every time your computer boots. However, in newer versions of Windows up to and including Windows 10, this feature is no longer available.

This it why Microsoft has created the Offline SFC, a way to run System File Checker before you log in to your computer. Here is what you have to do to run Offline SFC:

  1. Insert the Windows installation disc or USB flash drive, or a system repair disc, and then shut down your computer
  2. Restart your computer and when prompted press any key
  3. On the Install Windows page, or on the System Recovery Options page, choose your language and other preferences, and then click Next
  4. Click Repair your computer. Select the Windows installation you want to repair, and then click Next
  5. On the System Recovery Options menu lick on Command Prompt, then type in the following command and hit Enter:
sfc /scannow /offbootdir=d:\ /offwindir=d:\windows

Once SFC completes the repair, type Exit and reboot the system

How to resolve SFC initiation errors

As mentioned above, SFC is not perfect. Like all Windows services, it might encounter errors from time to time and an example is the “Windows Resource Protection Could Not Start the Repair Service” error.

To resolve this, you first need to check if your Windows Modules Installer Service is disabled. In the Start menu, type services.msc in the search bar. The status of this service should be set to Manual.

Of course, there are other possible errors that could occur while trying to run the System File Checker. Here is a list of examples:

  1. System File Checker SFC cannot repair corrupted member file. Microsoft suggests the following steps for this error:
  • At an elevated command prompt, type the following command, and then press ENTER:
takeown /f Path_And_File_Name
  •  Type the following command, and then press ENTER to grant administrators full access to the file: 
icacls Path_And_File_Name /GRANT ADMINISTRATORS:F
  •  Type the following command to replace the file with a known good copy of the file: 
Copy Path_And_File_Name_Of_Source_File Path_And_File_Name_Of_Destination
  1. Windows Resource Protection found corrupt files but was unable to fix some of them: Try running SFC in Safe Mode or run the command Dism /Online /Cleanup-Image /RestoreHealth in Command Prompt
  2. System File Checker not working, will not run or could not repair: Try running the command Dism /Online /Cleanup-Image /RestoreHealthin Command Prompt