CAPTCHA is not visible at frontend login/register form for RWD theme

Sadly the RWD theme has been implemented without captcha. See notes from the design guide section Exceptions to Responsive Web Design.

They have managed this by providing an empty layout.xml file for the captcha module under app/design/frontend/rwd/default/layout/captcha.xml. What you could try is to disable this file and so it will fall back to the default captach.xml and see if this works.

Sadly I have not tried this as yet.