failed to open stream..

below is the index.php file:
as far as I can see, the include statement is correct?
but I'm still getting these errors:
===============
alien@www [/etc/init.d]# php /home/shreemaa/public_html/httpdocs/drupal/index.php

Warning: main(./includes/bootstrap.inc): failed to open stream: No such file or directory in /home/shreemaa/public_html/httpdocs/drupal-4.7.3/index.php on line 12

Fatal error: main(): Failed opening required './includes/bootstrap.inc' (include_path='.:/usr/lib/php:/usr/local/lib/php:/php/includes:/home/shreemaa/public_html/httpdocs/drupal/includes') in /home/shreemaa/public_html/httpdocs/drupal-4.7.3/index.php on line 12
===============

===========index.php========
<?php
// $Id: index.php,v 1.90 2006/01/27 18:51:51 dries Exp $

/**
* @file
* The PHP page that serves all page requests on a Drupal installation.
*
* The routines here dispatch control to the appropriate handler, which then
* prints the appropriate page.
*/

require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$return = menu_execute_active_handler();
switch ($return) {
case MENU_NOT_FOUND:
drupal_not_found();
break;
case MENU_ACCESS_DENIED:
drupal_access_denied();
break;
case MENU_SITE_OFFLINE:
drupal_site_offline();
break;
default:
// Print any value (including an empty string) except NULL or undefined:
if (isset($return)) {
print theme('page', $return);
}
break;
}

drupal_page_footer();
=============