Try reinstalling the extension.. Maybe that will fix the activation issue.
I noticed you had an older version of the captcha include file.. Updating that to the latest version appears to have fixed it as well.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.