function check_downloads_form() {
    if ($('downloads_form_firstname').getValue() == "") {
        alert("Please enter your first name.");
        return;
    }
    if ($('downloads_form_lastname').getValue() == "") {
        alert("Please enter your last name.");
        return;
    }
    if ($('downloads_form_email1').getValue() != $('downloads_form_email2').getValue()) {
        alert("The email addresses don't match.");
        return;
    }
    if ($('downloads_form_email1').getValue().search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) == -1) {
        alert("This does not seem to be a valid email address.");
        return; 
    }
    $('downloads_register').value = '1';
    $('downloads_form').submit();
}