Corrupted Windows system files cause random crashes, failed updates, and broken features. The SFC and DISM tools can scan and repair them without reinstalling Windows. Here is how to use both correctly.
In this guide
Open Command Prompt as Administrator. Run: sfc /scannow. SFC compares every protected system file against a cached reference copy and replaces any corrupted ones. The scan takes 5-15 minutes. When complete, you will see one of three messages: no integrity violations found (all clear), repaired successfully (files were fixed), or unable to fix (DISM needed next).
If SFC reports it cannot fix files, the Windows component store itself is corrupted. Run DISM: DISM /Online /Cleanup-Image /CheckHealth — then DISM /Online /Cleanup-Image /ScanHealth — then DISM /Online /Cleanup-Image /RestoreHealth. RestoreHealth downloads clean component files from Windows Update. Run SFC again after DISM completes.
If SFC keeps finding the same corrupted files, they are being re-corrupted by a running process. Boot into Safe Mode (hold Shift while clicking Restart → Troubleshoot → Advanced Options → Startup Settings → Enable Safe Mode), then run sfc /scannow from there. Safe Mode prevents most drivers and third-party services from loading, which often allows SFC to complete repairs successfully.
After running SFC, open the log at C:\Windows\Logs\CBS\CBS.log. Search for "cannot repair" to find which specific files could not be fixed. You can manually replace these files by booting from a Windows installation USB and using the repair console, or by extracting the correct file version from a known-good Windows ISO.
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