How to Take Full Control of Windows Registry Key

If you want to modify a Registry key in Windows and you get the error "Access is Denied", means that the Registry key is protected by Windows. At this case and in order to resolve the problem, you need (first) to take the ownership of that particular registry key, and then, to assign full permissions to your user account at that key.

This guide, contains all the steps required in order to assign full permissions on a system protected registry key, in Windows 10, 8/8.1 or 7 OS.
Method 1: Take Ownership Using the Registry Editor
This is the old school way to take permission of any registry key in Windows 10 and other versions.
1. Open Registry Editor by pressing Windows key+ R, type regedit and hit Enter.

2. Navigate to the registry key that you want to take ownership of and Right-click on it.
3. Select the Permissions option.

4. In the permissions for the display window, click Advanced.

5. In the owner section, the key has Trusted Installer as the Owner. Click Change to change the owner.

6. In the new window, type your username and click Check Names button.

7. Select your username in the box and click OK to save the changes.
8. Check the Replace owner on subcontainers and objects checkbox and click Apply.

9. Again in the Permissions for Display window, select your username and check Full Control option in the Allow section.

10. Click Apply and OK to save the changes.
This should give you the full permission on the registry key.
Video:

Method 2: Take Ownership Using Command Line
SetACL makes it easy to grant full permission to any registry key in Windows 10. It is a third-party utility, and you need to download it onto your computer before you can use it.
1. Download SetACL from here. Make sure you download the executable (.exe) version for the administrator.
https://helgeklein.com/download/#setacl
2. Extract the downloaded file, and it will have both 32-bit and 64-bit version exe files. You need to use the version that is compatible with your PC.
3. Move the SetACL.exe file to C:\Windows\System32 folder. Simply copy and paste the file.
Note: It is not mandatory to move the SetACL.exe file to the Windows root folder as suggested above, but doing so will allow you to run the SetACL tool from anywhere without having to enter the path again and again while using the command prompt.
4. Open Command prompt as Administrator. To do this, Press Windows key + X and select Command Prompt (Admin) from the options.

5. Type the following command in the command prompt:
SetACL -on name -ot type -actn action
6. Hit Enter ↵ to execute.
7. Now you need to enter two commands followed by the registry key of which you want to take ownership. You need to change the registry key in the following command and keep everything else as it is. See the example below and later proceed with the command.
Example of the Registry Key to want to take Ownership: 
HKEY_CLASSES_ROOT\CLSID\{018D5C66-4533-4307-9B53-224DE2ED1FE6}

Command 1: It will make the administrator as the owner of the registry key.
SetACL.exe -on "HKEY_CLASSES_ROOT\CLSID\{018D5C66-4533-4307-9B53-224DE2ED1FE6}" -ot reg -actn setowner -ownr "n:Administrators"

Command 2: It will grant full permission to the administrator for the registry key.
SetACL.exe -on "HKEY_CLASSES_ROOT\CLSID\{018D5C66-4533-4307-9B53-224DE2ED1FE6}" -ot reg -actn ace -ace "n:Administrators;p:full"

That’s it. Now that you have taken ownership of registry key, you can proceed to edit the key.