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Most problems pertaining to Windows operating systems come from damaged files and corrupted system components. When a number of system files get corrupted, the programs and apps dependent on them fail to launch or run.

To fix these corrupted files, your Windows computer has a built-in tool called the System File Checker (SFC). It is developed by Microsoft as a utility that helps you scan your system files and fix the corrupted ones.

How to Use SFC Scannow

Here, you’ll learn all about the System File Checker tool and how you use the SFC scan to repair damaged system files on your Windows 10/8/7 computer.

What is System File Checker (SFC Scannow)?

Introduced with Windows 98, the System File Checker tool is a Microsoft Windows utility present in all succeeding Windows operating systems. With SFC, you can scan your system files systematically, detect the corrupted components, and get them repaired or restored.

You need a command-line interface to run or invoke System File Checker. Most commonly, the tool is run with

Command Prompt or Windows PowerShell.

When you feed in the command, Windows runs the SFC scan. During the scan, all system files on your Windows OS are examined and verified for their authenticity. If the scan detects a damaged or corrupt system file, the tool automatically fixes it.

Sometimes, the system file may be corrupted beyond repair. The SFC scan restores such file by replacing it with the identical, incorrupt file.

How to Run SFC Tool in Windows 10/8/7

To use the System File Checker tool, you need no additional downloads or any form of system upgrade. All the basic programs you need to run this utility are already ready on your Windows system.

In Windows 10/8/7, you can run the SFC scan with the help of Command Prompt. Follow the steps below to use SFC on your Windows computer.

  1. Go to the Start menu on your desktop
  2. In the search box, type ‘cmd’ or ‘command prompt
  3. From the top search results, select the Command Prompt program and right-click on it
  4. Now, click on Run as Admin or Run as administrator option from the dropdown menu
  5. Click on ‘Yes’ when the UAC prompt throws up
  6. The Command Prompt window opens
  7. Now, type the following command-line – sfc /scannow

How to Run SFC Tool in Windows 10/8/7

8. After typing it, press the Enter key

Now, your Command Prompt window shows the scan initiating. In the window, the messages “Beginning system scan” and “This process will take some time” will appear.

Moments later, the verification phase of the SFC scan begins. During this phase, do not turn off your PC or put it into sleep/hibernate mode.

You can also consider closing all the background/running apps and programs on your Windows system. This helps the scan to thoroughly check system files, without interfering with any ongoing processes.

Once the Verification is 100% complete, the scan proceeds to detecting the corrupted files.

If your Windows doesn’t have any corrupted files, you’ll read the message – Windows Resource Protection did not find any integrity violations.

When the SFC scan detects the corrupted files, it shows a message that reads –

Windows Resource Protection found corrupt files but was unable to fix some of them.

Followed by this, the message further informs that “Details (of the scan) are included in the CBS.Log windir\Logs\CBS\CBS.log.”

To view the contents of (parse) this .log file,

  1. Go to the Start menu and type ‘powershell’ in the search box
  2. Find the Windows PowerShell program, right-click on it and select Run as admin option from the menu
  3. Click on Yes from the UAC prompt
  4. Now, open the Windows PowerShell program
  5. Type the following command-line

Get-Content -Path windir\Logs\CBS\CBS.log

Get-Content -Path windir\Logs\CBS\CBS.log
  1. Press the Enter key

You can also open the .log file with the Notepad app.

Now, you can view the summary of the scan and identify the corrupted files that SFC was unable to repair. With this information, you can seek further technical assistance to fix the corrupted system files on your Windows PC.

System File Checker: How it Works

In Windows 10 and other latest versions (Win 7, Win Vista, etc.), the System File Checker tool is integral to the Windows Resource Protection utility. After the scan ends, it is the Windows Resource Protection utility that has detected and fixed the corrupted files, and not the SFC tool.

Technically, the SFC scan doesn’t fix the corrupted system files by itself. It uses the protocols and programming processes set by the Windows Resource Protection utility. This way, the registry keys, local group policy entries, and critical system files on your Windows system are well-protected during the scan.

So, what happens when you run an SFC scan?

System File Checker runs its scan through multiple phases. It examines system files across all system components in your Windows PC. Primarily, the SFC scan runs its course through –

  • DLLs (Dynamic Link Libraries)
  • SourcePath (for registry values)
  • ServicePackSourcePath
  • Access control lists

During the verification stage, a corrupted file is easily detected when it shows difficulty to launch. Such files are then pushed forward to the Windows Recovery Environment utility and the Deployment Image Service and Management (DSIM) tool. Here, the files that are not overly corrupted are repaired. Some corrupted files that are easily replaceable are restored in this stage.

Remaining, unrepaired files are further enlisted in a .log file. All SFC log files are permanently saved in their default location. You can view the SFC history of a Windows PC by going through these log files.

If you want to manually restore or fix the damaged files, you can also choose to stop the corrupted files from getting repaired automatically. Instead of using the “sfc /scannow” command, you can key in “sfc /verifyonly”. This command won’t repair the corrupted files, but a record of the detected damaged files gets stored in the log file.

Is System File Checker Helpful?

Yes, the SFC scan can surely save you money and effort for fixing corrupted system files. You don’t need to purchase third-party programs to repair damaged files on your Windows system.

For some Windows operating systems, you can also use the SFC scan by running the sfc.exe file or by executing a .bat file that contains the respective commands.

So, let us know how you used the SFC Scannow command on your Windows 10 system. Share your comments below.

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