Hide the whole forums to unregistred people
 

How do you make it so that people must register to view any part of the forums? If I just deny them permission in the user group they still can see the "What's going on portion". Basicly I want the user to either log in or Register before they can view the forums.

you could create a plugin at hook global_setup_complete where you check if the user is logged in or not and if not => print_no_permission();

Go to your Acp-Groups-Choose your guest group and clcik edit. Then under Forum Viewing Permissions set Can View Forum to No.

Thank you, but how to let the spiders indexing the content of the hiden forums ?

You don't... a spider is just an unregistered user- if you want to hide stuff from unregistered users you hide them from spiders as well. If I find something on google I should be able to view it without registering at a site to see it.

I'm not sure hiding everything from unregistered users is a good idea. What are you going to use to entice then? I would allow them to view some forums but not post so they will get a taste of what the site is about. Otherwise, you may lose more registrations than you will gain in the long run.