question

Hi @Joe-2522,

There are a few ways of upgrading your Windows 10 Pro to Windows 10 Enterprise, for example by the command-line tool:
Cscript.exe c:\windows\system32\slmgr.vbs /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

For more information, please refer to the official documentations below:

Windows 10 edition upgrade
https://docs.microsoft.com/en-us/windows/deployment/upgrade/windows-10-edition-upgrades

Windows 10 upgrade paths
https://docs.microsoft.com/en-us/windows/deployment/upgrade/windows-10-upgrade-paths

Here's also a detailed step-by-step guide:
How to Upgrade from Windows 10 Pro to Windows 10 Enterprise

If the reply was helpful please don't forget to upvote and/or accept as answer, thank you!

Best regards,
Leon

Hello @Joe-2522,

Initially Microsoft rejects the any upgrade from Windows 10 to LTSC as LTSC has some limitations regarding applications, so it is not an upgrade but kind of Downgrade. You can see it here: https://docs.microsoft.com/en-us/windows/deployment/upgrade/windows-10-upgrade-paths

In-place upgrade from Windows 7, Windows 8.1, or Windows 10 semi-annual channel to Windows 10 LTSC is not supported.

However, if you want to do some testing with the activation, from an elevated command promtp try:

-To remove any existing product key enter and run the command: slmgr.vbs /upk .
-Clear the product key from registry by running: slmgr.vbs /cpky
-Enter your new product key using the command: slmgr.vbs /ipk YOUR-PRODUCT-KEY-CODE
-Toactivate Windows by entering the command slmgr.vbs /ato and restart.

To check the activation status run: slmgr /xpr

Hope this helps with your query.
Best regards,

The business with slmgr.vbs did not work for me. It complained about the wrong SKU when I tried to put in a Windows 10 Enterprise LTSC product key.

Here's what I did to pull this off. This was moving from Windows 10 Pro to Windows 10 Enterprise LTSC 2021 in-place (version 21H2 in both cases).

• Open regedit and navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion
  

• Change "EditionID" to "EnterpriseS"
  

• Change "ProductName" to "Windows 10 Enterprise 2021 LTSC"
  

• Run setup.exe from Windows 10 Enterprise LTSC 2021 install media and perform an in-place upgrade. (With the registry change it should allow you to keep "all apps and files".)

Note that the EditionID and ProductName registry entries will revert to their old values after some time, so be sure to kick off the setup process promptly once you make the changes.

This would be fully unsupported by Microsoft but it seemed to work fine for me.

You can use a similar trick to perform other unsupported in-place upgrades (for example, moving from Windows 10 Pro to Windows 10 Home). Change "EditionID" and "ProductName" to what they should be on the OS that you want to move to, and then kick off an in-place upgrade using that install media. Your system will be "not activated" after the upgrade is finished and you'll need to provide a proper product key.

I doubt that you can safely "downgrade" to an older Windows 10 version using this method. You won't be able to move to Windows 10 Enterprise LTSC 2019 in-place if you have a Windows 10 version higher than 1809 installed. If Microsoft releases a 22H2 version next year, upgrading to it might make an in-place upgrade to 2021 LTSC (based on 21H2) impossible.