How to Repair Corrupted Windows System Files with SFC and DISM

When Windows starts behaving strangely – settings pages that won’t open, features that crash, updates that fail, or error messages about missing DLL files – corrupted system files are a common culprit. Windows includes two free tools to fix them: DISM (Deployment Image Servicing and Management) and SFC (System File Checker). Used together, they resolve a surprising number of problems without reinstalling Windows.

What the two tools do

• SFC scans all protected Windows system files and replaces any that are damaged or modified with a correct copy.
• DISM checks and repairs the component store – the folder of original files (WinSxS) that SFC copies from. If the component store itself is damaged, SFC can’t fix things on its own.

That’s why the recommended order is DISM first, then SFC.

Before you begin

• You need an account with administrator rights.
• DISM’s repair option downloads clean files from Windows Update, so stay connected to the internet.
• Close other programs and plug in laptops – the process can take a while.
• If the PC belongs to your employer, check with IT first; managed devices may use different update sources.

Step 1: Open an elevated terminal

1. Right-click the Start button.
2. Choose Terminal (Admin) (on some versions, Windows PowerShell (Admin) or Command Prompt (Admin)).
3. Select Yes in the User Account Control prompt.

Both PowerShell and Command Prompt can run these commands.

Step 2: Run DISM

Run the three DISM checks in order. The first two only check; the third repairs.

DISM /Online /Cleanup-Image /CheckHealth

This is a quick check of whether corruption has already been recorded.

DISM /Online /Cleanup-Image /ScanHealth

This performs a more thorough scan and takes several minutes.

DISM /Online /Cleanup-Image /RestoreHealth

This scans again and repairs any problems it finds, downloading replacement files from Windows Update. When it finishes, you should see “The restore operation completed successfully.”

Many people skip straight to /RestoreHealth, which is fine – it includes the scan. Running the first two is helpful when you want to know whether corruption existed before repairing.

Step 3: Run SFC

Now run the System File Checker:

sfc /scannow

The scan goes through several stages and usually takes 5–15 minutes. Don’t close the window until it reaches 100%.

Step 4: Understand the results

SFC ends with one of these messages:

Details of what SFC found are written to %windir%\Logs\CBS\CBS.log. The file is large and technical, but searching it for “[SR]” shows the SFC entries.

Step 5: Restart and test

Always restart after repairs – some replaced files are only loaded at startup. Then try whatever was failing before.

If DISM fails

DISM can fail if Windows Update itself is broken or blocked. Common causes and fixes:

• No internet or a firewall blocking Windows Update – check your connection and any third-party security software.
• Windows Update components damaged – follow the reset steps in our Windows Update troubleshooting guide, then try again.
• Use installation media as the repair source – advanced users can mount a Windows ISO of the same version and language and point DISM to it with the /Source option, as described in Microsoft’s DISM documentation. Create media with our guide to making a Windows 11 installation USB.

When to consider other options

If SFC and DISM both report success but problems continue, the cause is probably not system file corruption. Look at recently installed apps or drivers, use System Restore if a restore point exists, or consider Settings › System › Recovery › Reset this PC (choosing Keep my files). If you see disk errors or the PC is freezing, check the health of the drive as well – failing storage can corrupt files repeatedly.

Conclusion

DISM and SFC are safe, built-in tools that every Windows user should know. Run DISM /Online /Cleanup-Image /RestoreHealth first, then sfc /scannow, restart, and test. Together they fix a wide range of “Windows is acting weird” problems without touching your personal files.