Captcha upon login

[bigs15]

Hey guys i am trying to acc captcha protection for 3.8.7 vbulletian forum. I tried very much but failed
I tried this code in header login area.
The Standard Challenge and Non-JavaScript API,

<script type="text/javascript"
     src="http://www.google.com/recaptcha/api/challenge?k=your_public_key">
  </script>
  <noscript>
     <iframe src="http://www.google.com/recaptcha/api/noscript?k=your_public_key"
         height="300" width="500" frameborder="0"></iframe><br>
     <textarea name="recaptcha_challenge_field" rows="3" cols="40">
     </textarea>
     <input type="hidden" name="recaptcha_response_field"
         value="manual_challenge">
  </noscript

>

It show the recaptcha box.But forum looks ugly so i tried regex method of recaptcha buts not working.

The reCAPTCHA AJAX API

<script type="text/javascript" src="http://www.google.com/recaptcha/api/js/recaptcha_ajax.js"></script>

      <!-- Wrapping the Recaptcha create method in a javascript function -->
      <script type="text/javascript">
         function showRecaptcha(element) {
           Recaptcha.create("your_public_key", element, {
             theme: "red",
             callback: Recaptcha.focus_response_field});
         }
      </script>

    <div id="recaptcha_div"></div>

      <input type="button" value="Show reCAPTCHA" onclick="showRecaptcha('recaptcha_div');"></input>

Doc: https://developers.google.com/recaptcha/docs/display
Here is the document.Can some one tell me how i can add ? In this big forum there is no plugin for captcha during login lol.So i am trying to make tutorial if i sucess.