That's just closing up the board, I think ThreadsUser wants to do a complete whipe of the userdatabase.

What do you want to do with existing posts?

If you want to clear up your board to a full new reset, you could drop all your database tables and run install/createtable.php. This would recreate the tables and allows you to add your admin account again.

Be sure to save all your customized styles before you do that.

[Linked Image from siemons.org]