SFC — System File Checker

Opens an elevated Command Prompt and run:

sfc /scannow

This scans all protected system files and replaces corrupted ones from a cached copy. Takes 10–20 minutes.

DISM — when SFC fails

SFC cannot fix files if the component store itself is corrupt. DISM repairs the store first:

DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth

RestoreHealth downloads replacement files from Windows Update — requires internet.

Run SFC again after DISM

After DISM completes, run sfc /scannow again. This time it should succeed because the component store is repaired.

Reading SFC results

Check C:WindowsLogsCBSCBS.log for details. Search for "Cannot repair" — those files need an in-place repair upgrade.