wprock on "How to activate a widget at sidebar without use WP-ADMIN->Widget UI"

Hi ALL,

I need a help. I want to activate the registered widget using PHP script at my sidebar (without use WP-ADMIN->WIDGET UI). Have any hook for this in WP? Any one know it?. When I am installing the WP 3.3.1 first, I am getting 5 activated widgets at my sidebar automatically. I need exact that functionality.

Thanks