We are running CiviCRM 4.5.3 on Joomla! 3.3.3.
As the question says, we want to know how to stop people who haven't paid (pending from pay later or incomplete transaction) from filling an event.
If, for example, an event is set for 16 registrants and 15 have booked and paid and 1 is still pending from pay later, then bookings close. No one can book online; it says the event is full.
We don't want that to happen. We want anyone who is pending from pay later or an incomplete transaction to NOT count towards the total registrants for the course.
In this way, what we want to do is enable someone to come along, book online and pay immediately, and take the place of anyone who hasn't paid yet.
This used to be how it worked in our old version of CiviCRM, so we know it's possible!