'Notify user of new account' checkbox to be selected as default
found here - http://drupal.org/node/1295268#comment-5060488

&lt;?php
function MODULE_NAME_form_alter(&amp;$form, $form_state, $form_id){
    if ($form_id == 'user_register') {
        $form['account']['notify']['#default_value'] = TRUE;
    }
}
?&gt;