try running the following SQL statement to create the admin username and passwpord:
INSERT INTO wa_settings (name, type, options, value, grp, subcategory, cond, description, variable, weight, spry_args, spry_error, help_text)
VALUES
('admin_username', 'text', '', 'admin', 'Site', NULL, NULL, '', 'Admin_Username', 72, ', \"none\", {isRequired:true, validateOn:[\"blur\", \"change\"]}', NULL, 'This is the Administrative Username that should be reserved for the website developer. Only this user will be able to modify the details of the Settings page. Additional administrative accounts can be created under the \'Users\' section of the PowerCMS Admin - these users will not be able to modify these settings.'),
('admin_password', 'text', '', 'test123', 'Site', NULL, NULL, '', 'Admin_Password', 73, NULL, NULL, NULL)");