Form redirection to registration for anonymous users while preserving data entered
One option would be to do this in a custom module with hook_form_alter(). You could use it to alter the CCK form to add a custom validation/submit handler that redirects anonymous users to the registration page. The inserted form data could be stored in the session (before redirecting) from where you can retrieve it later to fill in the form with default values (using hook_form_alter() again). I'm assuming that you do not need to store the data for long periods of time since session is not suitable for that. You should also unset the used session variables after use.