Error message

• User warning: The following module is missing from the file system: rules_admin. For information about how to fix this, see the documentation page. in _drupal_trigger_error_with_delayed_logging() (line 1181 of /home/ainold/_OLDAIN/docroot/includes/bootstrap.inc).
• User warning: The following module is missing from the file system: rules_admin. For information about how to fix this, see the documentation page. in _drupal_trigger_error_with_delayed_logging() (line 1181 of /home/ainold/_OLDAIN/docroot/includes/bootstrap.inc).