CiviCRM 2.1 and reCaptcha configuration settings.

If you get this message while test driving an event in CiviCRM 2.1
"To use reCAPTCHA you must get an API key from http://recaptcha.net/api/getkey"
 
After registering for your key, you can configure the site settings by navigating to:
  1. Admin
  2. Administer CiviCRM
  3. Configure
  4. Global Settings
  5. Miscellaneous Settings
Scroll down to reCaptcha Keys and enter your public and private keys