How to add a registration form in admin section

I want to add a registration form like Administrator Users->Users. The content should be stored in a new table. Should I do this using API or using extending some class if it is done using extending some class how could I do this please help me. I read the code flow of adding users it uses some core class like oxuser should I develop a code similar to this and putting a core code on this duplicating all including template to make my requirement.