One option for you is to leave the registration on, but then assign all new registrations a group that has no access or assign them to the guest account.  Then even if someone registers, they still can't see anything unless you edit their profile.  Just make sure the default group has no access to whatever you want to hide.

You could save yourself a lot of work that way.  I had a similar situation where I set-up a forum for students in my class.  I told them to register themselves.  When they registered, they were put into the default members category which give them no access and certain areas were invisible to them.  I then verified that they were a student registering, and then changed their group to the student group that allowed them access to the hidden areas.

That would save you a lot of typing and set-up and still block out unauthorized people.  It also allows them to pick their own passwords, etc.

You might want to try that method instead.