When Windows system files are missing or corrupted, it can result in Windows crashes, slow startups or problems with installing Windows updates. In these cases, we can use the SFC /SCANNOW command to repair the files. But before you use the SFC command, it’s important that you first run the DISM command . If that completes without errors, only then you can continue with SFC. In this article In this article, I will explain how to use the SFC Scan commands, when to use them, and when it absolutely doesn’t make sense to use it at all. How to use SFC /SCANNOW As briefly mentioned in the beginning, before you can use the System File Checker command, you will need to make sure that your Windows component store, that is the place where Windows keeps a clean copy of the system files, is not corrupted. If your Windows component store also has corrupt files, then the SFC scan command won’t be able to repair your Windows system files. So the first step is to run the DISM command. Step 1 – Run DISM Command To run the commands in Windows 11, you need to open an elevated PowerShell or Terminal (Admin): Right-click on Start Open Terminal (Admin) Enter the command below and press Enter. Wait for it to complete before you continue: When it completes without any error, only then can we continue with the SFC /SCANNOW command. If you do get an error, then read this article , where I explain how you can solve them easily. Step 2 – Run SFC /SCANNOW With the DISM command completed, we can run the System File Checker command to actually repair the corrupted Windows files. To run the command, we also need to use the elevated PowerShell or Terminal (Admin) Type the following command and press enter: The System File Checker will scan all system files and replace corrupted files with a copy from the Windows component store. When the scan is complete,d you will get one of the following messages: Running SFC /SCANNOW in Safe Mode Quite often, the System File Checker can’t repair corrupted files because they are in use by Windows or other programs. You will then see the result message Windows Resource Protection could not perform the requested operation. To solve this, you will need to run the command again in safe mode. In safe mode, Windows only loads the essential drivers and services, so fewer files are locked or in use. This gives SFC full access to repair corrupted system files. Hold down the Shift key while clicking on Power -> Restart in the Start Menu (or see this article with other options, like holding F8 during booting your comptuer) Go to Troubleshoot > Advanced Options and open Command Prompt Now we are going to run the SFC scan command, but a bit differently. If we would just run SFC /SCANNOW directly in the command prompt, it would actually scan the Windows Recovery Environment, instead of your Windows installation. So instead, you will need to run the command below to point the scan to your Windows installation: Now the drive letter can sometimes be different, so if you get a message that it can’t find the resource, then just change the drive letter to D:\ for example. Again, it will take 10 to 15 minutes to finish, just get a coffee or go for a walk, and let it complete. Fixing “Corrupt files but was unable to fix some of them” Sometimes the System File Checker isn’t able to repair every file. You will then get the result message Windows Resource Protection found corrupt files but was unable to fix some of them . This error means that Windows was not able to replace one or more corrupted files automatically. Now, the first thing you should check is if the DISM command completes without any issues. Because we need to make sure we have a good version of the file. If DISM completes without issues, we will need to replace the corrupted files manually. First, we need to find out which files SFC couldn’t repair, and then replace them with a version from a healthy system. Step 1 – Find which files to replace First, we need to export the SFC result into a readable format. Run the command below to export all entries from the system file checker: Open the sfcdetails.txt file on your desktop. Every entry marked with [SR] is from the system file checker scan. Look for the entries from your last scan and note the files that SFC couldn’t repair. They are listed together with their full path. Step 2 – Replace the corrupted files Now we know which file(s) is damaged, we can start to replace it. The health version must come from a computer running the exact same version of Windows. Next, you need to take ownership of the corrupted file and grant yourself full access: Make a copy of the good file to a USB drive and bring the file over to the computer with the corrupted version. Replace the corrupt file: When done, restart the computer and run sfc /scannow again. If the file was the cause of the issue, the scan should complete without errors. If it still fails, or if more files show up as unrepaired, then you have a more complicated problem. At that point, an in-place repair install, or clean Windows installation might be the fastest way forward. Fix SFC SCANNOW Stuck Sometimes the SFC scan gets stuck at a certain percentage. This doesn’t mean your computer froze. It means SFC can’t continue because it’s running into a file that Windows can’t read or access. There are a couple of common causes for this: The disk contains errors A system file is locked by a driver or service The Windows component store is corrupted There are memory issues

To fix this, follow the steps below If the disk has bad sectors or file system errors, then System File Checker can get stuck. Run the command below in an elevated Terminal (admin) and restart the computer: This will scan the entire disk for errors and repair them when possible. It can take a while, especially on HDDs. After the scan completes, run: 2. Run DISM First If the Windows component store is corrupted, then SFC can’t continue. As mentioned in the beginning of the article, make sure that the DISM command completes without errors. When it completes without errors, restart the computer and try SFC again. 3. Run SFC in Safe Mode Drivers or services can lock system files, which prevents SFC from reading or replacing them. Running SFC in Safe Mode normally solves this. Restart your computer while holding Shift , open Troubleshoot , and open Command Prompt . Run the command below, pointing SFC to your actual Windows installation: 4. Check for Memory Problems Faulty memory can also cause SFC to stop. Open the Start Menu and run Windows Memory Diagnostic . Choose Restart now and check for problems . If memory issues are found, fix those first before running SFC again. 5. Try an Offline Scan from USB or Recovery Media If the system is too unstable, boot from Windows installation media and run SFC from there. Use the same command: Offline scans often repair files that fail during normal boot. After completing these steps, SFC should no longer get stuck and the scan should finish normally. If it still freezes at the same percentage, then you’re likely dealing with deeper corruption. In that case, an in-place repair install of Windows is usually the quickest way to solve the problem. SFC Commands Switches Besides the well-known SFC /SCANNOW command, there are a couple of other useful options. You won’t need them often, but they can be helpful when you want to verify a single file, schedule a scan at boot, or run SFC offline. Below you will find a complete overview of all SFC command switches. On most systems the scan takes 10 to 15 minutes. On older hardware or slow hard drives it can take longer. As long as the percentage continues to move from time to time, the scan is still running. You can safely stop the scan, it won’t damage Windows, but it also won’t fix anything. The scan will simply end without applying all repairs. Just run it again and let it finish normally. Always run DISM first. DISM repairs the component store, and SFC depends on this store to replace corrupted files. If the component store is damaged, then SFC can’t fix anything. DISM first, then SFC. Technically you can, but it’s better not to. SFC needs access to system files, and active applications can slow it down or lock files. Let it finish without doing anything else on the computer is the best option. You don’t run SFC on a schedule. Only use it when Windows behaves strangely, crashes, or fails to install updates. If the system runs fine, then there is no need to run it. No. SFC itself does not cause problems. If it reports errors that it cannot fix, then the system was already corrupted. SFC only reveals the issue, it doesn’t create it. Sometimes yes. If the first scan repairs some files, then a second scan can continue and repair the rest. If you want to be sure, run SFC twice after DISM completes. Yes. SFC is part of Windows and only repairs protected system files. It does not touch personal files or application data. You can run it without worrying about losing anything. The SFC /SCANNOW command is often recommended as the magic tool to fix all Windows problems. That is not true, but when Windows updates won’t install, or your system randomly crashes, then it’s a good and easy place to start. It won’t do any harm, and any corrupted file will be found and if possible, be repaired. Just make sure you first run the DISM command. Hope this article helped you, if you have any questions, just drop a comment below. Enjoying the article but hate the ads? Join the Insiders for a clean, ad-free experience ($1) , or go Elite ($3) to get priority answers and more. You may also like the following articles September 2026 update Break RDS – How to Fix From PowerShell Scripts to Building an Automation Platform Free OST to PST Conversion Online: Stellar Converter Review 1 thought on “How to Use SFC /SCANNOW – The Complete System File Checker Scan Guide” folks, Since last few days I’m getting message “Access denied” while open files like “pdf,xlsx,txt,docs” in certain folder, I already did many attempts using various command from internet but still facing issue, please fix it remotely, if possible, I will pay for so. Usama 9879969666 folks, Since last few days I’m getting message “Access denied” while open files like “pdf,xlsx,txt,docs” in certain folder, I already did many attempts using various command from internet but still facing issue, please fix it remotely, if possible, I will pay for so. Usama 9879969666 Enjoying the article but hate the ads? Join the Insiders for a clean, ad-free experience ($1) , or go Elite ($3) to get priority answers and more. Leave a Comment Cancel reply So, about that AdBlocker... Will you consider disabling it? Yes, ads can be annoying. But they allow me to keep writing content like this. You can also support me by becoming an Insider ($1) for a ad-free experience or Buy Me a Coffee ☕ | Read more about disabling AdBlockers