[Plugin: SI CAPTCHA Anti-Spam] Use any where captcha

I would also like to know this answer.

In my case, I have the login form embedded on a different page using this method – http://www.wprecipes.com/add-a-login-form-on-your-wordpress-theme

The form works fine without the plugin enabled. With it enabled, the captcha doesn’t show on my embedded login, and you are redirected to the main login page where an error message says the captcha is incorrect. Perhaps I need to add a bit of code for the hook to work properly?

This plugin is not designed as an API for any form you install. It only works on the the WordPress forms for comments, registration, lost password, and login.

For contact form needs, use this plugin for your forms.
http://wordpress.org/extend/plugins/si-contact-form/