Theming a custom form I have themed Drupal7 forms, cannot do the same with 6 ...

I have:

function _my_form() {
    $output="";
    $form=drupal_get_form("my_form");
    $output=theme("my_form",
        array(
            "element"=&gt;array(
                "my_form"=&gt;$form
            )
        )
    );

    return $output;

}

function MYMODULE_theme()
{
    $themes = array(
        'MY_form' =&gt; array(
            'template'=&gt;'my_form',
            'variables' =&gt; array('element' =&gt; NULL)
        )
    );
    return $themes;
}


If i do a var_dump($element["my_form"]) in my_form.tpl.php i only get a superlong string with the html form already rendered, while i expected to have an array with all the single form fields... what am i doing wrong?
i think you should return a  render array in your theme function 
  array('render element' => 'form')