I wasn't talking about the people on the members list, if you look at the bottom of the main page of the forum you will see a box that says "What's Going On?".
In that box it says "Currently Active Users:XX (x members and xx guests)." Look at the members listed there, these are the members that are registered and online, if you click on one of those names a box will pop open showing the members Join Date and the number of posts they have. You want to target the members with "0" posts.