Fatal error

hi im new using this module, when i enable this module..i got this error. anybody can help me ?? thanks

Fatal error: Cannot redeclare user_delete() (previously declared in /var/www/vhosts/slank.com/httpdocs/modules/user/user.module:1599) in /var/www/vhosts/slank.com/httpdocs/forum/includes/functions_user.php on line 586