How to Fix Windows 10 0xc000021a Error After Booting from External Windows 11 USB Flash
If you are encountering the 0xc000021a error on your Windows 10 computer after booting from an external Windows 11 USB flash drive, don't worry. This error can be frustrating, but there are several steps you can take to resolve it. In this guide, we will walk you through the troubleshooting process to help you fix the issue and get your system up and running again.
Step 1: Disconnect the External USB Flash Drive
The first thing you should do is disconnect the external USB flash drive that you used to boot into Windows 11. Sometimes, this error occurs due to compatibility issues between Windows 10 and Windows 11. By removing the USB flash drive, you can eliminate this potential cause.
Step 2: Restart Your Computer
After disconnecting the USB flash drive, restart your computer. This step can help resolve any temporary issues that may be causing the error. Simply click on the Start menu, select the Power icon, and choose Restart.
Step 3: Perform a Startup Repair
If the error still persists after restarting your computer, you can try performing a startup repair. Follow these steps:
- Insert your Windows 10 installation media (DVD or USB) into your computer.
- Restart your computer and boot from the installation media.
- On the Windows Setup screen, select your language preferences and click Next.
- Click on the "Repair your computer" link at the bottom left corner of the screen.
- Select Troubleshoot, then Advanced options, and finally Startup Repair.
- Follow the on-screen instructions to complete the startup repair process.
Step 4: Run System File Checker (SFC) Scan
If the startup repair didn't fix the error, you can try running a System File Checker (SFC) scan. This scan will check for any corrupted system files and attempt to repair them. Here's how to do it:
- Press the Windows key + X and select Command Prompt (Admin) to open an elevated Command Prompt.
- Type
sfc /scannowand press Enter. - Wait for the scan to complete. It may take some time.
- If any corrupted files are found, the SFC scan will attempt to repair them automatically.
- Once the scan is complete, restart your computer and check if the error is resolved.
Step 5: Perform a System Restore
If the previous steps didn't fix the error, you can try performing a system restore. This will revert your computer's settings to a previous state when it was working correctly. Here's how to do it:
- Press the Windows key + X and select System.
- In the System window, click on "System protection" in the left pane.
- Click on the System Restore button.
- Follow the on-screen instructions to choose a restore point and initiate the system restore process.
- Wait for the process to complete and then restart your computer.
By following these steps, you should be able to resolve the 0xc000021a error on your Windows 10 computer after booting from an external Windows 11 USB flash drive. If the issue still persists, it is recommended to seek further assistance from a professional technician or Microsoft support.
References
| Number | Source |
|---|---|
| 1 | https://www.windowscentral.com/how-use-system-restore-windows-10 |
| 2 | https://support.microsoft.com/en-us/windows/start-your-computer-in-safe-mode-in-windows-10-92c27cff-db89-8644-1ce4-b3e5e56fe234 |
| 3 | https://support.microsoft.com/en-us/windows/use-a-fix-it-tool-with-windows-10-7e5e8a65-2f62-0a94-dc81-7f6c7d3f1b3f |