User experience after registration

When a user registers, all he gets is the message "Thanks for creating account.", and the registration form is still visible. This is confusing for many of our users.

Possible solutions:

a) Remove the registration form after registration so that the user sees only the "Thanks for creating account." message and the login form. He then needs to log in manually.

b) Log the user in automatically and redirect him to the dashboard. (Preferred solution)