This is how I solved my problems with Captcha functionality in Drupal. Read ahead if you have experienced problems with the standard Captcha and Riddler modules. 

A while ago I migrated to Drupal 5.1. It was a quite effortless and painfree experience, but on the other hand this site is not relying on that many extra modules. One functionality that I can't do without though is the captcha function in order to combat spambots.

After installing Drupal I continued straight away to install the Captcha module; available at http://drupal.org/project/captcha [1]. At the time of the installation there was no official release for 5.1 so I had to go with the development snapshot. And sure it worked, but instead of presenting a distorted image to the user a mathematical problem was to be solved, ie something like what is the result of 3 + 5?

Unfortunately there are som spambots that solve this question as well and when checking the approval queue I found a bunch of spam from the people bot. Some solved this by adding the riddler module, a enhancement to the Captcha module, that allows the site manager to ask a somewhat harder question to answer, well for machines that is, with a question of your choice, like: How mAny capitAl A's Are there in this question? And the user is supposed to answer with the correct number in order to be able to post.

For some reason I never got it to work. I started with installing the Riddler module and enabling it. When directing the browser to http://mysite/admin/settings/captcha/riddler [2] I was able to administer the Riddler. But that was the only way to reach the administration interface of the module. There were no tabs or menu options to access the module what so ever. The module didn't even show up in the drop down menu on the Captcha administration page. I don't seem to be alone regarding this problem, other have reported similar errors.

I figured that it might have to do with the use of the development snapshot of Captcha so I installed the latest and greatest version of the module; captcha-5.x-2.1. Well, this seemed a bit more promising but when trying it out I was always told that I had answered the question wrong. The Riddler or Captcha seemed a bit flaky so I pursued another track.

During my effort to solve the problems with the Captcha and Riddler modules I had run into  an alternative module called MyCaptcha [3] developed by Heine Deelstra. Said and done, I installed it and it worked without a fuzz immediately. And it even offers the solution that I was using in the first place, a distorted text as an image. This module needs the Form Store [4] module so be sure to install and enable it.

If you happen to add more forms to your site you might want to add captcha functionality to those as well. For example my contact page wasn't included among the forms in the administration interface of the captcha module. But that was easy solved by enabling the Form Collect module and then turn form collect on. It's located as a tab when administering Form Store. Check the box so that forms will be collected when browsing the site and then steer your browser to the form you want to add. After that I turned Form Collect off. Now, the contact form was available on the Captcha administration interface.

Now, there is no spam anymore in the approval queue.