404 error loading admin page

Url - www.offerusaprice.co.uk

Hi All,
i have sucessfully installed Zencart and my shop is working but when i try www.offerusaprice.co.uk/admin I get Error 404 page. i don't know what to try next.
this is what it says in my admin/includes/configure.php

<?php
/**
* @package Configuration Settings circa 1.3.8
* @copyright Copyright 2003-2007 Zen Cart Development Team
* @copyright Portions Copyright 2003 osCommerce
* @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
*/

/*************** NOTE: This file is similar, but DIFFERENT from the "store" version of configure.php. ***********/
/*************** The 2 files should be kept separate and not used to overwrite each other. ***********/

// Define the webserver and path parameters
// Main webserver: eg-http://www.your_domain.com -
// HTTP_SERVER is your Main webserver: eg-http://www.your_domain.com
// HTTPS_SERVER is your Secure webserver: eg-https://www.your_domain.com
// HTTP_CATALOG_SERVER is your Main webserver: eg-http://www.your_domain.com
// HTTPS_CATALOG_SERVER is your Secure webserver: eg-https://www.your_domain.com
/*
* URLs for your site will be built via:
* HTTP_SERVER plus DIR_WS_ADMIN or
* HTTPS_SERVER plus DIR_WS_HTTPS_ADMIN or
* HTTP_SERVER plus DIR_WS_CATALOG or
* HTTPS_SERVER plus DIR_WS_HTTPS_CATALOG
* ...depending on your system configuration settings
*
* If you desire your *entire* admin to be SSL-protected, make sure you use a "https:" URL for all 4 of the following:
*/
define('HTTP_SERVER', 'http://www.offerusaprice.co.uk');
define('HTTPS_SERVER', 'https://derby.eukhost.com/signifypromotions_co_uk');
define('HTTP_CATALOG_SERVER', 'http://www.offerusaprice.co.uk');
define('HTTPS_CATALOG_SERVER', 'https://derby.eukhost.com/signifypromotions_co_uk');

// Use secure webserver for catalog module and/or admin areas?
define('ENABLE_SSL_CATALOG', 'true');
define('ENABLE_SSL_ADMIN', 'true');

// NOTE: be sure to leave the trailing '/' at the end of these lines if you make changes!
// * DIR_WS_* = Webserver directories (virtual/URL)
// these paths are relative to top of your webspace ... (ie: under the public_html or httpdocs folder)
define('DIR_WS_ADMIN', '/admin/');
define('DIR_WS_CATALOG', '/');
define('DIR_WS_HTTPS_ADMIN', 'https://www.offerusaprice.co.uk/admin/');
define('DIR_WS_HTTPS_CATALOG', 'https://www.offerusaprice.co.uk/');

define('DIR_WS_IMAGES', 'images/');
define('DIR_WS_ICONS', DIR_WS_IMAGES . 'icons/');
define('DIR_WS_CATALOG_IMAGES', HTTP_CATALOG_SERVER . DIR_WS_CATALOG . 'images/');
define('DIR_WS_CATALOG_TEMPLATE', HTTP_CATALOG_SERVER . DIR_WS_CATALOG . 'includes/templates/');
define('DIR_WS_INCLUDES', 'includes/');
define('DIR_WS_BOXES', DIR_WS_INCLUDES . 'boxes/');
define('DIR_WS_FUNCTIONS', DIR_WS_INCLUDES . 'functions/');
define('DIR_WS_CLASSES', DIR_WS_INCLUDES . 'classes/');
define('DIR_WS_MODULES', DIR_WS_INCLUDES . 'modules/');
define('DIR_WS_LANGUAGES', DIR_WS_INCLUDES . 'languages/');
define('DIR_WS_CATALOG_LANGUAGES', HTTP_CATALOG_SERVER . DIR_WS_CATALOG . 'includes/languages/');

// * DIR_FS_* = Filesystem directories (local/physical)
//the following path is a COMPLETE path to your Zen Cart files. eg: /var/www/vhost/accountname/public_html/store/
define('DIR_FS_ADMIN', 'D:/inetpub/vhosts/offerusaprice.co.uk/httpdocs/admin/');
define('DIR_FS_CATALOG', 'D:/inetpub/vhosts/offerusaprice.co.uk/httpdocs/');

define('DIR_FS_CATALOG_LANGUAGES', DIR_FS_CATALOG . 'includes/languages/');
define('DIR_FS_CATALOG_IMAGES', DIR_FS_CATALOG . 'images/');
define('DIR_FS_CATALOG_MODULES', DIR_FS_CATALOG . 'includes/modules/');
define('DIR_FS_CATALOG_TEMPLATES', DIR_FS_CATALOG . 'includes/templates/');
define('DIR_FS_BACKUP', DIR_FS_ADMIN . 'backups/');
define('DIR_FS_EMAIL_TEMPLATES', DIR_FS_CATALOG . 'email/');
define('DIR_FS_DOWNLOAD', DIR_FS_CATALOG . 'download/');

// define our database connection
define('DB_TYPE', 'mysql');
define('DB_PREFIX', '');
define('DB_SERVER', 'localhost');
define('DB_SERVER_USERNAME', '*****');
define('DB_SERVER_PASSWORD', '*****');
define('DB_DATABASE', 'signifyp_1');
define('USE_PCONNECT', 'false');
define('STORE_SESSIONS', 'db');
// for STORE_SESSIONS, use 'db' for best support, or '' for file-based storage

// The next 2 "defines" are for SQL cache support.
// For SQL_CACHE_METHOD, you can select from: none, database, or file
// If you choose "file", then you need to set the DIR_FS_SQL_CACHE to a directory where your apache
// or webserver user has write privileges (chmod 666 or 777). We recommend using the "cache" folder inside the Zen Cart folder
// ie: /path/to/your/webspace/public_html/zen/cache -- leave no trailing slash
define('SQL_CACHE_METHOD', 'none');
define('DIR_FS_SQL_CACHE', 'D:/inetpub/vhosts/offerusaprice.co.uk/httpdocs/cache');

// EOF