Would like to separate 2 node types on registration, also fieldgroup not showing up

I am creating a site for a charity. Would like to expand on the default profile fields and also add a section to the registration form that allows for people to volunteer at the same time.

I have created 2 content types (user profile, volunteer application) and have included them on the registration form. However, there is no separation of the forms (ie. there is no indication that the person is now filling out the registration area which should only be done if they want to register).

I have followed the advice of a poster on the forums and tried using a fieldgroup, then dragging my other fields underneath. However, the title of the fieldgroup doesn't show up in either the original content type or the registration form. I haven't yet discovered how to include items within the fieldgroup (rather than just dragging various fields underneath) so I guess that could be why it isn't showing up? How do you do that?

What would be absolutely ideal would be to use a tab or maybe panels. But just having a separate section with a title would be okay too. Is this possible at all with Content Profile?

Thanks,

Shrill