You'll notice that the standard phpNuke CAPTCHA display here has been replaced by reCAPTCHA, which you may have seen on other sites like Craigslist. For those of you not familiar with reCAPTCHA, it looks like this:

and is a great spambot fighter. Read this article on what reCAPTCHA is and how it works.
In order to fight the increased number of spambots on this site, I installed reCAPTCHA in place of the standard CAPTCHA during account registration. If you want this done on your site, submit a paid support request. The fee is a flat $25 for the installation.