same issue as this thread:
www.joomlapolis.com/forum/118-captcha/152967-problem-viewing-captcha-image

but then on Joomla 1.7 with CB 1.7 and captcha Version 2.4.

in the plugin config the preview does not display the image.

Plugin Prerequisites
Captcha Requirements: GD: bundled (2.0.34 compatible)
Freetype: enabled

Sample Rendering (based on settings)

I set 'Captcha images and sound mode:' to 'index.php'.

I am migrating a site from 1.5.23 where the image is displaying properly on the same localhost-server, so I guess the image-libraries used are installed ok (WAMP). On the old site I got Joomla 1.5.23, CB 1.7 and captcha Version 2.2.1.

I got it.

The captcha image is called using index2.php, which is deprecated in Joomla 1.7. In file components/com_comprofiler/plugin/user/plug_cbcaptcha/cb.captcha.php change both instances of 'index2.php' to 'index.php', and it works again.

testing, testing, testing

I tried editing the file changing index2.php to index.php (both instances), but I still cannot get the image or sound prompts to show? Nant, I cannot find your reference;

have you moved your Joomla config file?

please try changing the last parameter: Use Joomla index

Help please