Adding field to the client registration form and back office

[andresdelosreyes]

Hi, I need to add a new field to customer, something like a Social Security number, this needs to be on
the create account page, and also on the customer edit/create new customer in the back office so it can
be editable, how can I do this pleas help. I know I have to edit som .php and .tpl files but I don't know
which ones to edit, any help is welcome!!!

Thanks in advance

Andres de los Reyes