BuddyPress.org

In your BuddyPress settings:
Settings > BuddyPress > Pages
Be sure you have set up your pages.

Be sure Registration is enabled
Settings > General> Check Anyone Can Register

Also, if you are logged in, your Registration page will default to your home page. If you want to remain logged in, just open a different browser, i.e. if you are in FireFox, open IE and you should see your Registration form.