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How to Repair Corrupted System Files (SFC & DISM)

✅ Quick Answer

Corrupted system files can cause crashes, slow performance, errors, and Windows instability. The best way to repair them is by running SFC /scannow and DISM /RestoreHealth. SFC scans and repairs damaged Windows files, while DISM fixes the Windows image used by SFC. If both tools fail, using Windows Repair or reinstalling Windows may be required.

❓ Why System Files Get Corrupted?

System files can become corrupted due to sudden shutdowns, power failure, malware, bad updates, failed installations, or disk errors. When Windows cannot access important system files, you may face errors like “App won’t open”, “Windows Update fails”, or frequent crashes.

Corrupted files also cause performance issues and can prevent your PC from starting properly. The good news is that Windows includes built-in tools to repair these files without reinstalling the OS.

🔧 Fix 1: Run SFC /scannow (System File Checker)

SFC scans Windows system files and replaces corrupted files with a cached copy stored on your PC. This is the most common and safest method to repair system issues.

  1. Open Command Prompt as Administrator.
  2. Type the command below and press Enter:
sfc /scannow
  1. Wait for the scan to finish (can take 10–20 minutes).
  2. After completion, check the result message:

Restart your PC after SFC completes. If SFC couldn’t fix everything, move to the next step.

🔧 Fix 2: Run DISM /RestoreHealth (Repair Windows Image)

DISM fixes the Windows image, which SFC uses to repair corrupted files. If SFC fails, DISM is the next solution.

  1. Open Command Prompt as Administrator.
  2. Type the command below and press Enter:
DISM /Online /Cleanup-Image /RestoreHealth
  1. Wait for the process to finish (can take 15–30 minutes).
  2. After DISM finishes, run sfc /scannow again.

DISM may download files from Windows Update, so ensure you have a stable internet connection.

🔧 Fix 3: Use SFC in Safe Mode (If Normal Mode Fails)

If your PC has serious corruption or apps blocking SFC, running SFC in Safe Mode helps because fewer services are running.

  1. Press Windows + I → System → Recovery.
  2. Under Advanced startup, click Restart now.
  3. Go to Troubleshoot → Advanced options → Startup Settings.
  4. Click Restart and choose Safe Mode.
  5. Open Command Prompt and run sfc /scannow again.

Safe Mode reduces interference from third-party apps, increasing success rate for repairs.

🔧 Fix 4: Repair Windows Using Installation Media (If DISM Fails)

If DISM fails due to corrupted Windows Update components, using installation media is the final fix. This method repairs the Windows image from the installation files.

  1. Download the Windows Media Creation Tool from Microsoft.
  2. Create a bootable USB or ISO.
  3. Open Command Prompt as Administrator.
  4. Run DISM with the source path:
DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:X:\Sources\Install.wim:1 /LimitAccess

Replace X: with your USB drive letter. This method is more powerful and fixes deep system corruption.

🔧 Fix 5: Check Disk for Errors (Fix File System Issues)

Disk errors can cause file corruption. Running CHKDSK repairs disk problems that may cause system file damage.

  1. Open Command Prompt as Administrator.
  2. Run:
chkdsk C: /f /r

If the disk is in use, Windows will ask to schedule on next restart. Press Y and restart your PC.

❓ Frequently Asked Questions

How long does SFC /scannow take?

Usually 10–20 minutes. It depends on system speed and disk size. Do not interrupt the process.

What is the difference between SFC and DISM?

SFC repairs corrupted system files using local cache. DISM repairs the Windows image, which SFC relies on.

Can these commands delete my files?

No. SFC and DISM only repair system files and do not delete personal data.

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Last updated: January 2026 • Techfix&Guides