administrator with ownership trying to change permission Ultimate

Vista Ulitimate.On installing a program I am confronted with a message."could
not open key Hkey_local_machine\software etc.. Verify that you have
sufficient access to that key.
I have waded through security for this software to change permission. I have
achieved changing ownership to administrator but have lost the thread at
changing permission for the object in this case the Program that gives me
suffiecient access to that Hkey. I imagine I should be able to gain full
control over security of this program to get rid of this message blocking my
installation progress but I don't understand the final steps to gain full
control.