Change only the installed Microsoft PowerToys startup setting or application implicated by this sign-in error. The report does not establish a cause for other Explorer file-system errors.

  • A File system error -1073479340 from explorer.exe appeared at logon while the PC otherwise worked.
  1. Open Settings > Apps > Installed apps.
  2. Uninstall Microsoft PowerToys, or first disable PowerToys automatic startup if preserving the app.
  3. Restart Windows.
  4. Verify the explorer.exe file-system error no longer appears.

Reported outcome: The original poster said deleting PowerToys made the error disappear; another participant confirmed disabling autostart fixed the same error.

Prefer the reversible startup-setting test when retaining the application. Re-enable the recorded setting if the error persists, and preserve the exact error/build for further diagnosis.