[development] How can I customize user registration page?

Hi all, I'm trying to customize user registration page by profile module. But the fields I set by profile module are placed in another filedset, not the same fieldset email and password fields are placed in. How can I place them in the same fieldset ? to use hook_form_alter() ? Are there any functions like phptemplate_user_profile() to be overridden for user registration page style? Thank you, Huisi