Widget plugin WordPress 2.3

Hello,

I’m getting the following error when I try to activate the widget plugin..

Plugin could not be activated because it triggered a fatal error.

Fatal error: Cannot redeclare register_sidebars() (previously declared in /home/.stilts/michaelsync/michaelsync.net/wp-includes/widgets.php:15) in /home/.stilts/michaelsync/michaelsync.net/wp-content/plugins/widgets/widgets.php on line 42

After reading some posts, this error occurs because this plugin is already included wordpress core by default….

So, if I wanna customize the widget plugin, how can I do that???