How to fix Error 571 on Windows 11

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Windows Error 571: {Privilege Failed} — I/O Permissions Could Not Be Changed

Why This Error Happens

Error 571 occurs when a process attempts to modify its I/O privilege level (IOPL) but lacks the necessary token privileges to do so, typically because it isn’t running with sufficient administrative rights. This is common with legacy applications, hardware diagnostic tools, or drivers that require direct hardware I/O port access, a capability tightly restricted by Windows 11’s security model. It can also occur if User Account Control (UAC) is blocking the elevation request or if the application’s manifest doesn’t properly request elevated privileges.

Step-by-Step Resolution Guide

  1. Run the Application as Administrator
    Right-click the application’s .exe file (or shortcut) and select Run as administrator. This grants the process the elevated token needed to request I/O privilege changes.

  2. Set Permanent Elevation via Compatibility Settings

  • Right-click the executable → Properties → Compatibility tab.
  • Check Run this program as an administrator.
  • Click Apply, then OK.
  1. Check and Adjust UAC Settings
  • Open Control Panel → User Accounts → Change User Account Control settings.
  • Lower the slider to “Notify me only when apps try to make changes to my computer” (avoid disabling UAC entirely for security reasons).
  • Restart the application and confirm the elevation prompt appears and is accepted.
  1. Verify Group Policy / Local Security Policy Restrictions
  • Press Win + R, type secpol.msc, and press Enter.
  • Navigate to Local Policies → User Rights Assignment.
  • Locate “Increase scheduling priority” and “Load and unload device drivers” — ensure the user account or group running the app is listed under these policies.
  • Reboot after making changes.
  1. Update or Reinstall the Driver/Application
    If the error stems from a legacy hardware tool, check the vendor’s website for a Windows 11–compatible version. Older 32-bit drivers using direct port I/O (via _inp/_outp calls) are often blocked by kernel patch protection (PatchGuard) and may require a signed, updated driver.

Alternative or Verification Steps

  • Verify the fix: Open Event Viewer (eventvwr.msc) → Windows Logs → Application, and confirm Error 571 no longer appears after relaunching the app with elevated permissions.
  • Alternative: If the app still fails, run it in Compatibility Mode for an earlier Windows version (Properties → Compatibility → Run this program in compatibility mode for → select Windows 8/7), which can resolve legacy I/O privilege conflicts.