How to fix error 0x00000021 in Windows 11

Solution Steps

1. 1 Boot into Safe Mode to isolate the issue. Restart your PC and press F8 (or Shift + Restart) to access Advanced Boot Options. Select 'Safe Mode with Networking'. If the error doesn't occur in Safe Mode, a third-party driver is likely the cause.
2. 2 Run the Windows Memory Diagnostic tool to check for RAM issues. Press Windows key + R, type 'mdsched.exe', and press Enter. Choose 'Restart now and check for problems'. This will test your RAM for errors, as faulty memory can cause quota underflow.
3. 3 Update or roll back drivers, especially graphics and chipset drivers. Press Windows key + X and select 'Device Manager'. Look for devices with a yellow exclamation mark. Right-click and select 'Update driver' or 'Properties' → 'Driver' → 'Roll Back Driver' if the issue started after a driver update.
4. 4 Run SFC and DISM to repair system files. Open Command Prompt as administrator and run 'sfc /scannow' followed by 'DISM /Online /Cleanup-Image /RestoreHealth'. This fixes corruption that might be causing the error.
5. 5 Check for Windows updates and install them. Press Windows key + I, go to Windows Update, and click 'Check for updates'. Updates often include fixes for memory management issues.
6. 6 If the error persists, perform a clean boot to identify the problematic service. Press Windows key + R, type 'msconfig', and press Enter. In the Services tab, check 'Hide all Microsoft services' and click 'Disable all'. Then restart. If the error stops, enable services one by one to find the culprit.