Creating the user profile whenever a user is created

I have enabled the CCK account profile on a drupal installation, and have added some fields to the profile. I can see the profile fields whenever I edit a user but cannot see them when I want to create a user. In fact when a new user is added its profile is always null.
How can I make the profile fields show up when creating a user? I will be even more happy if the profile is a required value and the profile cannot be null.