use the same form that you have just replace the action from the email address to the following :
action="mail.php"
put the following script in a file names mail.php
<?
$header = "From: MyWebsite.com\r\n";
$header .= "Reply-To: $email\r\n";
$header .= "MIME-Version: 1.0\r\n";
$header .= "Content-Type: text/html; charset=iso-8859-1\r\n";
$header .= "X-Priority: 1\r\n";
$header .= "X-Mailer: PHP / ".phpversion()."\r\n";
$extra = "Reply-To: $email\r\n";
$subject = "Booking";
$mess = "<u><center>MyWebsite.com - Online Booking</center></u><br><br>Booking For Class : <b>$classname</b><br><br>First Name : <b>$firstname</b><br>Last Name : <b>$lastname</b><br>Username : <b>$username</b><br><br><br>Password : <b>$password</b><br>E-Mail Address : <b>".$email."</b>";
mail("myemail@mydomain.com", $subject, $mess, $header);
echo("Thanks. Your E-mail Has Been Sent.<br><br><a href=\"".$HTTP_REFERER."\">Go Back.</a>\n");
?>
and then try it out
Damian