that error has to do with the settings.php
Looking at the installer, it looks like the settings.php is made only after everything is installed.
PHP Code:
<?php
$my_base_url = 'http://localhost';
$my_pligg_base = '/pligg';
$dblang = 'en';
define('table_prefix', 'pligg_');
include_once mnminclude.'settings_from_db.php';
?>
here's settings.php. just edit with your details and see how it goes.