If you're talking about personal messages then it's up to each person if they want to accept them or not. Being registered is not the issue. Go to your "IN" box and click "Preferences" and you will see where you can select to get or not to get PM's for this board. Also, if you use "enhanced topics" as a default start page you may never see that you have a PM unless you go to the main page.
Just send Skip an E-mail.