mssql connect to php:Call to undefined function mssql_connect()

Actually, now I only test my webpage in a computer that I create as a server. And also I’m not too familiar in a server. Now I created a database in SQL Server 2005 Express and some of information I will share is:

I used:
SQL Server 2005 Express
IIS 6.0
Php 5.2.14

Server Type: Database Engine
Server name: ComputerName\SQLEXPRESS
Authentication: Windows Authentication
Username: NETBIOS NAME\Administrator [hide]
Password: [hide]

My problem is I cannot connect to my database using php and I don't know what username and password I should use if the Username: NETBIOS NAME\Administrator Password: [no password]

This is my php code:
[PHP]
<?php
//session_start();
//session_regenerate_id();

//if($_SESSION['loggedin']){
//the user is already logged in, lets redirect them to the other page
// header("Location:company.php");
//}


$server = "Computer Name\SQLEXPRESS";
$user = "NETBIOS\Administrator";
$pass = "";
$db_name="dbase";

//connection to database
$dbhandle = mssql_connect($server, $user, $pass) or die ("Cannot connect to Server");

//mssql_connect($server, 'sa', 'pass') or die("Cannot connect to server");
$selected = mssql_select_db($db_name, $dbhandle)or die("Cannot select DB");


$department = $_POST['department'];
$username = $_POST['username'];

$sql=mssql_query("SELECT `Department`, `Username` FROM `tbl_user` WHERE `Department` = '{$department}' AND Username = '{$username}'") or die(mssql_min_error_severity());
$ct = mssql_num_rows($sql);

if($ct == 1) {
// im guessing this means that the user is valid.
$_SESSION['loggedin'] = true; // now that the user is valid we change the session value.
$row = mssql_fetch_assoc($sql);

//$_SESSION['username'] = $row['Username'] ;
//$_SESSION['department'] = $row['Department'];

$Departments=array('Accounting', 'Engineering', 'Finishing_Goods', 'HRAD', 'MIS', 'Packaging_and_Design', 'Production', 'Purchasing_Logistic', 'QA_and_Technical', 'Supply_Chain');

if (in_array($row['Department'], $Departments)){
header ('Location:company.php');
}else{
echo "Incorrect Username or Department";
header ('Location:index.php');
}
}
?>

[/PHP]

I don't know if what configuration i need to do to work my connection. I configured php.ini like:

I uncommented the following:

extension_dir = "C:\php\ext"
extension=php_sqlsrv_52_ts_vc6.dll
extension=php_bz2.dll
extension=php_curl.dll
extension=php_dba.dll
extension=php_exif.dll
extension=php_gd2.dll
extension=php_gettext.dll

mssql.allow_persistent=On
mssql.max_persistent=-1
mssql_max_links=-1
mssql.min_error_severity=10
mssql.compatibility_mode=Off
mssql.connect_timeout=5
mssql.timeout=60
mssql.textlimit=4096
mssql.textsize=4096
mssql.batchsize=0
mssql.datetimeconvert=On
mssql.secure_connetion=Off

FreeTDS default to 4096
mssql.max_procs=25
mssql.charset = "ISO-8859-1"

After I commented out that in php.ini, I put all sqlsrv file in C:\php\ext and the ntwdlib.dll into C:\WINDOWS\system32. After that still when I run my webpage the error is still there. I have no idea how I can fix that error.


Error:
Fatal error: call to undefined function mssql_connect() in C:\Inetpub\wwwroot\web_intranet\index.php on line 17

I hope somebody can help or tell me what I should do.
Thank you