I keep trying to enter my serial number into Statbook and it keeps telling me it not valid. I've tried manual entry and copy/paste.

First check that you are using version 3.0 or higher (About Statbook menu item). If it's 2.x, a 3.0 serial number will not work as this was not a free upgrade. If you need a 2.x serial number, please use the following form: http://statbook.pachysoft.com/php/LostRegistrationNumber.php