In Current System

My Users input their real long name in User Name field when register.

Because there don't exist screen name field.

so. i often manually change username field -> user id.

so i want make screen name filed top position,not in custom field area.

or

user can modify there username where user cp.

how can i do it?

I would like to have this feature as well and i've seen it somewhere... just can't remember where it was :(

May be someone has a hack for this?