Having a problem, with setting a default group, for new members

Hey, Was wondering if you could help me.

On my forums, I have lots of different categories, relating to different games, etc. What I want however, is for a group to be defaulted, so that the member, has to request access, to view the rest of the categories. I know this is possible on other forums, but i can't seem to find the option anywhere in amongst the administration panel.

Can anyone help me in this matter?

Thanks

Egg Fried Cheese (ENO Gaming)