WordPress 2.3 Contact Form Captcha

I had a client who needed to add a captcha to their contact form in WordPress. Only problem was, they were running WordPress 2.3 which was very outdated, and for other reasons they couldn’t upgrade. I found this one and only plugin which has CAPTCHA and keeps its older versions in stock.  Contact Form 7 version 1.5 does the trick quite nicely. :)