I was trying to avoid getting this detailed about the situation, but here's the whole story:
I started a free site about 18 months ago and had around 5,000 members sign up. Then 12 months ago, we moved to a paid subscription model. Using a program called aMember to manage our payments and members, anyone who chose to not pay the subscription was cut off. When someone registers for my site, they do so through aMember, which checks their email address and username for uniquness in the ubbt database. If no record is found, they are allowed to proceed, complete the signup, and are placed into a paid member group. If their email address is found in the db, they are told that they have been a member in the past and must use a different form to re-register. The whole process is rather confusing. I am trying to avoid all of this by removing anyone who initially did not pay to become a member so that if they do come back, the db treats them as a new customer.
This is the reason I need to flush all of these members out, only leaving the paid members.