Regedit "Cannot Delete" "Error while deleting key"

You probably have to take ownership before you can delete the key. Right click on the key and click "Permissions...", then Add. Type in your username then "Check Names". Click OK. Then Click Advanced and then the Owner tab. Highlight your username and hit OK. You should now be able to check Full Control under the Allow column and from there actually delete the key.

Edit: You can also check the "Advanced" permissions with the list of "Permission entries" to see if there are any "Deny" types preventing deletion.

I have found the answer. There was a driver preventing the deletion. I used the notepad backdoor to delete it (has not been tested on OS subsequent to Windows 7).

Note: If you already have a Windows Recovery drive, you can delete the driver by booting from the drive, opening the Command Prompt, and deleting it using some simple Batch commands (or starting notepad and navigating with an interface from Open on the file menu).

Directions:

1. Restart your computer.
2. When you see the Starting Windows screen, force shutdown your computer.
3. Start your computer.
4. You should see a menu with a Launch Startup Repair (recommended) option. Select this.
5. Startup Repair will now start. You will shortly see a window saying Do you want to restore your computer using System Restore?. Click cancel.
6. Wait until another window pops up (this may take a while) that says Startup Repair cannot repair this computer automatically. Click on the View problem details drop-down.
7. Scroll down to the last link (it should be a text file) and click on it.
8. Once in notepad, click Open from the file menu. From there you have full access to your computer.

For deleting a driver, navigate to C:\Windows\System32\drivers and delete the driver you want.

If you know Batch, navigate to C:\Widnows\System32 and right click on cmd.exe. Click Run as administrator.