CAPTCHA Anti-Robot

Had a problem with tell a friend section of the software.
Robot attacked and sent out over 1,000 e-mails (I recieved copies as the admin.

Just Upgraded to : v1.3.9c 5/27/2010
I have No add addons that I know
Checked out the following site link in Zen Cart site concerning my problem

http://www.zen-cart.com/index.php?main_page=product_contrib_info&cPath=40_47&products_id=325

The latest Version: 0.99.137 which states is good for Zen Cart™ Version: v1.3.7.

I believe that I can't use this on my new update does anyone know of a newer release or another way of solving the problem

New Directions:

Had a problem with tell a friend section of the software.
Robot attacked and sent out over 1,000 e-mails (I recieved copies as the admin.

Just Upgraded to : v1.3.9c 5/27/2010
I have No add addons that I know
Checked out the following site link in Zen Cart site concerning my problem

http://www.zen-cart.com/index.php?main_page=product_contrib_info&cPath=40_47&products_id=325

The latest Version: 0.99.137 which states is good for Zen Cart™ Version: v1.3.7.

I believe that I can't use this on my new update does anyone know of a newer release or another way of solving the problem

It would have to be merged into the 1.3.9 files, should be too difficult to do. There are only 4 files to be merged, the rest can be used as is.
To be merged are:
includes/modules/create_account.php
includes/modules/pages/create_account/header_php.php
includes/modules/pages/create_account/jscript_form_check.php
includes/templates/template_default/templates/tpl_modules_create_account.php

It was a simple thing to do. I will upload it to the file section but if you want it quickly, send me a PM