Dism /Online /Cleanup-Image /RestoreHealth
Both will restore modified & corrupted system files. So, you can lose your overzealous windows customizations. Ideally, it should not change non-Microsoft programs & settings, still depending on the level of corruption!
- If you are so concerned about your customizations, You can just run scans
Dism /Online /Cleanup-Image /ScanHealth
They will just check the files without any repair process ( as here & here ). Analyze the log/ report & decide.
- DISM /Online /Cleanup-Image /RestoreHealth
is not available for win 7. ( DISM commands are very limited on win 7)
- & You can always make System Image ( Macrium Reflect ) before that!