I am not really sure what this thread is about - I am assuming you must be discussing older versions of dnn - the current version of dnn (4.3 and later), allows complete customisation of the user profile and registration, without any coding

Use Manage Profile Properties on the Users module to manage the profile properties you would like to use - there are only 4 required properties (LastName/FirstName/TimeZone?Preferred Locale).  You can add/edit/delete profile properties and recategorise them to change the grouping behaviour.  If you are a developer you can create "new" profile datatypes.

If you then go to User Settings (again from the Users Module) you can manage multiple options with regard to the profile and registration.

I have written a few articles on the Profile Editor which you cna find here.