Access denied

Hi

I have successfully installed Drupal but i am unable to login.If i click on something i get the 'access denied' Message.My username is 'root' and i dont have any password.whenever i click login it displays a msg 'password field is required'.This is how my 'Settings.php' looks like -
<?php
// $Id: settings.php,v 1.39 2007/01/14 02:05:15 unconed Exp $

/**
* @file
* Drupal site-specific configuration file.
*
* IMPORTANT NOTE:
* This file may have been set to read-only by the Drupal installation
* program. If you make changes to this file, be sure to protect it again
* after making your modifications. Failure to remove write permissions
* to this file is a security risk.
*
* The configuration file to be loaded is based upon the rules below.
*
* The configuration directory will be discovered by stripping the
* website's hostname from left to right and pathname from right to
* left. The first configuration file found will be used and any
* others will be ignored. If no other configuration file is found
* then the default configuration file at 'sites/default' will be used.
*
* For example, for a fictitious site installed at
* http://www.drupal.org/mysite/test/, the 'settings.php'
* is searched in the following directories:
*
* 1. sites/www.drupal.org.mysite.test
* 2. sites/drupal.org.mysite.test
* 3. sites/org.mysite.test
*
* 4. sites/www.drupal.org.mysite
* 5. sites/drupal.org.mysite
* 6. sites/org.mysite
*
* 7. sites/www.drupal.org
* 8. sites/drupal.org
* 9. sites/org
*
* 10. sites/default
*
* If you are installing on a non-standard port number, prefix the
* hostname with that number. For example,
* http://www.drupal.org:8080/mysite/test/ could be loaded from
* sites/8080.www.drupal.org.mysite.test/.
*/

/**
* Database settings:
*
* Note that the $db_url variable gets parsed using PHP's built-in
* URL parser (i.e. using the "parse_url()" function) so make sure
* not to confuse the parser. If your username, password
* or database name contain characters used to delineate
* $db_url parts, you can escape them via URI hex encodings:
*
* : = %3a / = %2f @ = %40
* + = %2b ( = %28 ) = %29
* ? = %3f = = %3d & = %26
*
* To specify multiple connections to be used in your site (i.e. for
* complex custom modules) you can also specify an associative array
* of $db_url variables with the 'default' element used until otherwise
* requested.
*
* You can optionally set prefixes for some or all database table names
* by using the $db_prefix setting. If a prefix is specified, the table
* name will be prepended with its value. Be sure to use valid database
* characters only, usually alphanumeric and underscore. If no prefixes
* are desired, leave it as an empty string ''.
*
* To have all database names prefixed, set $db_prefix as a string:
*
* $db_prefix = 'main_';
*
* To provide prefixes for specific tables, set $db_prefix as an array.
* The array's keys are the table names and the values are the prefixes.
* The 'default' element holds the prefix for any tables not specified
* elsewhere in the array. Example:
*
* $db_prefix = array(
* 'default' => 'main_',
* 'users' => 'shared_',
* 'sessions' => 'shared_',
* 'role' => 'shared_',
* 'authmap' => 'shared_',
* 'sequences' => 'shared_',
* );
*
* Database URL format:
* $db_url = 'mysql://username:password@localhost/databasename';
* $db_url = 'mysqli://username:password@localhost/databasename';
* $db_url = 'pgsql://username:password@localhost/databasename';
*/
$db_url = 'mysql://root:@localhost/sample';
$db_prefix = '';

/**
* Base URL (optional).
*
* If you are experiencing issues with different site domains,
* uncomment the Base URL statement below (remove the leading hash sign)
* and fill in the URL to your Drupal installation.
*
* You might also want to force users to use a given domain.
* See the .htaccess file for more information.
*
* Examples:
* $base_url = 'http://www.example.com';
* $base_url = 'http://www.example.com:8888';
* $base_url = 'http://www.example.com/drupal';
* $base_url = 'https://www.example.com:8888/drupal';
*
* It is not allowed to have a trailing slash; Drupal will add it
* for you.
*/
# $base_url = 'http://www.localhost/drupal-5.1'; // NO trailing slash!

/**
* PHP settings:
*
* To see what PHP settings are possible, including whether they can
* be set at runtime (ie., when ini_set() occurs), read the PHP
* documentation at http://www.php.net/manual/en/ini.php#ini.list
* and take a look at the .htaccess file to see which non-runtime
* settings are used there. Settings defined here should not be
* duplicated there so as to avoid conflict issues.
*/
ini_set('arg_separator.output', '&');
ini_set('magic_quotes_runtime', 0);
ini_set('magic_quotes_sybase', 0);
ini_set('session.cache_expire', 200000);
ini_set('session.cache_limiter', 'none');
ini_set('session.cookie_lifetime', 2000000);
ini_set('session.gc_maxlifetime', 200000);
ini_set('session.save_handler', 'user');
ini_set('session.use_only_cookies', 1);
ini_set('session.use_trans_sid', 0);
ini_set('url_rewriter.tags', '');

/**
* We try to set the correct cookie domain. If you are experiencing problems
* try commenting out the code below or specifying the cookie domain by hand.
*/
if (isset($_SERVER['HTTP_HOST'])) {
$domain = '.'. preg_replace('`^www.`', '', $_SERVER['HTTP_HOST']);
// Per RFC 2109, cookie domains must contain at least one dot other than the
// first. For hosts such as 'localhost', we don't set a cookie domain.
if (count(explode('.', $domain)) > 2) {
ini_set('session.cookie_domain', $domain);
}
}

/**
* Variable overrides:
*
* To override specific entries in the 'variable' table for this site,
* set them here. You usually don't need to use this feature. This is
* useful in a configuration file for a vhost or directory, rather than
* the default settings.php. Any configuration setting from the 'variable'
* table can be given a new value.
*
* Remove the leading hash signs to enable.
*/
# $conf = array(
# 'site_name' => 'My Drupal site',
# 'theme_default' => 'minnelli',
# 'anonymous' => 'Visitor',
# );

Please tell me if there is anything wrong in it.

Abhishek