Sometimes it works to remove an entry in the registry by trying to change permissions. Go to the entry in the left hand pane of Registry Editor and left click on it. A screen will pop up that shows an entry called "permissions". Open it and go to "advanced" where you can try and take "full control" of the key. Like I mentioned sometimes it works and sometimes it doesn't, but maybe someone more knowlegable than me can give you further aid.
One more thing. You probably know this already, but I always make a backup of my registry before tinkering with things.