Follow the instructions below. If anything is unclear, just ask first.
Click Start typ regedit in the searchbox and press enter.
Allow the program to run.
"Registry-editor" will open. On the leftside browse to the key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages\Package_36_for_KB3075220~31bf3856ad364e35~x86~~6.1.1.0
Rightclick on it and select Permissions.
A new window opens, click the button Advanced.
A new window opens, select tab Owner.
Put a checkmark at Replace owner on subcontainers and objects
Select Administrators (...) then click Apply and OK.
In the list "Group or user names" select Administrators (...).
Next, put a checkmark to allow "Full Control" and click OK.
Rightclick the registry-key again and click Delete.
Are you able to delete the key ?