Attempted developing a simple wordpress plugin.

<?php
/**
 * @package Hello_Dolly
 * @version 1.6
 */
/*
Plugin Name: FomXong
Plugin URI: http://wordpress.org/extend/plugins/hello-dolly/
Description: This is not just a plugin, it symbolizes the hope and enthusiasm of an entire generation summed up in two words sung most famously by Louis Armstrong: Hello, Dolly. When activated you will randomly see a lyric from <cite>Hello, Dolly</cite> in the upper right of your admin screen on every page.
Author: Matt Mullenweg
Version: 1.6
Author URI: http://ma.tt/
*/
class My_Widget extends WP_Widget {
    function My_Widget() {
        // widget actual processes
    }

    function form($instance) {
        // outputs the options form on admin
    }

    function update($new_instance, $old_instance) {
        // processes widget options to be saved
    }

    function widget($args, $instance) {
        // outputs the content of the widget
    }

}
register_widget('My_Widget');
?>

When run this error is displayed. Why???? Fatal error: Call to some member function register() on the non-object in D:AppServwwwwptwp-includeswidgets.php online 431