How activate Privatemsg Module to all users? I just enabled the Privatemsg Module in my Drupal 6. I would like to enable this module to all users, who join in the website. But the registered users cannot see the "Write new message and Messages" link.

Why the  Privatemsg is not active in users section ?
You should change permissions for the Privatemsg module for authenticated users or whatever role you want in the permissions page(admin/user/permissions)

See http://drupal.org/getting-started/6/admin/user/permissions