We now see a huge influx of users upgrading to Windows 11. As before, the latest built Windows 11 Operating System is not free of errors. Recently many users complained that they were trying to reinstall and upgrade Windows 11; they encountered an activation error 0xC004C003 and became helpless to complete the process.

The main reason for this error is trying to activate Windows 11 on your PC using the OEM Activation Digital Product Key. If this product key access is denied, you will receive an error code 0xC004C003 on the screen. Another reason for this error is that the failure of key validation. If you are also experiencing the same error, you can rely on the solutions provided in this article. Let’s have a look.

Fix 1: Verify your Windows Edition:

While reinstalling Windows 11, you installed Pro edition instead of Home edition (Generally system comes with Home edition), you couldn’t activate Pro edition using the Home edition license key you are having. In this case, you will get the Activation Error 0xC004C003 on Windows 11. Here you need to check your Windows version. To do so,

  • Firstly, press Windows + I altogether to launch the Settings app.
  • Inside the Settings window, select System and click on the About option.
  • Then in the newly opened window, scroll down and select the Windows specification section from the right-pane menu.
  • And select Edition and see your Windows 11 edition.
  • If your installed edition is Pro and you have Windows 11 Home edition license key, then you need to downgrade the edition.

Fix 2: Downgrade from Windows 11 Pro to Windows Home Edition

In two ways, you can downgrade from Windows 11 Pro to Windows Home Edition.

Method 1: Edit Registry Editor:

  • Firstly, press Windows + R simultaneously to launch the RUN dialog box, type Regedit and click on the OK button.
  • If a UAC prompt appears on the screen, click on Yes.
  • Then inside the Registry Editor, go to the below path,
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion
  • Now from the right side of the screen, double-click on the ProductName option.
  • In the newly appeared prompt, type Windows 11 Home Single Language and click on the OK button.
  • Then scroll down and double click on EditionID value.
  • Again in the newly prompt window, type CoreSingleLanguage and click on OK.
  • Now go to the following path, 
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion
  • Then open ProductName Value and edit it to Windows 10 Home and click on OK.
  • And then double-click on EditionID and edit it to CoreSingleLanguage and click on OK.
  • Once done, exit from the Registry Editor and check for improvement.

Method 2: Downgrade using ISO file:

You can also downgrade Windows Home edition using an ISO file and perform an in-place upgrade. To do so,

Note: This method will help you to reinstall Windows OS without losing your files and apps.

  • Firstly, go to the official website of Microsoft and select Windows 11 Disk Image (ISO).
  • Then from the drop-down optionselect Windows 11.
  • Now click on the Download button.
  • There select the Language and click on Confirm and click on the 64-bit download button.
  • Once the download process gets completed, double click on it to open.
  • Then select and right-click on the ISO image and select Mount from the drop-down menu.
  • Now the driver folder will open automatically. 
  • If not, then you need to click on the DVD icon under This PC.
  • Then you need to select and double-click on the setup.exe file in the ISO folder.
  • In the newly opened window, select the Change how Setup downloads updates option and select Not right now.
  • Now click on the Next button and accept notices and license terms.
  • In the next window, select Install Windows 11 Home and select Keep personal files and apps.
  • Finally, click on the Install button. This process might take a few minutes to get complete, so please be patient.

To activate Windows 11 Home edition,

  • Firstly, go to the Settings app and select System.
  • Then select the Activation option and follow the on-screen instructions.

Fix 3: Use Command Prompt Window:

In case Microsoft fails to activate and verify due to a server issue, then you need to activate it using a command. To do so,

  • Firstly, type cmd in the search box and open the Command Prompt window with Administrative access.
  • Inside the Command Prompt window, type or copy then paste the following command and then press Enter,
slmgr.vbs –rearm
  • Once done, restart the system and check the said error disappeared on the screen.

Fix 4: Connect Microsoft to Activate Windows:

When you first register for Windows 11, it automatically associates to your device’s hard drive. Now the Microsoft ensure the license is used as per the Terms of Use, as well as users don’t have to activate Windows every time after a clean install.

You have recently replaced the motherboard, and Windows is not checking for validity. Here you need to use the digital product key or run the Troubleshooter to activate and validate Windows.

These are all about resolving the Activation Error 0xC004C003 on Windows 11. However, if you have any queries or doubts after reading this article, then please leave a comment in the below-given comment box.