Did you try launching the registry editor with administrative credentials?
Open the registry editor by clicking

and typing
regedit.exe into the search box. Next, either right click on the program and click
Run as administrator or simply press
Ctrl +
Shift +
Enter/
Return. Provide administrative credentials when prompted. This is because the key in question is in the
HKLM branch, and to modify the contents of this area of the registry it needs to invoked with administrative privileges.
Now try deleting the key.