Upgrades from 2.3 to 2.4 are free. If you are upgrading from version 2.3 of any of our security products to version 2.4, simply replace your old product with the new one. The upgrade will automatically use your previous settings. It will also use your previous serial numbers, unless you are upgrading from a very old version of the DoorStop X Firewall (version 2.2 or earlier), in which case you will need to purchase and enter a new serial number within 30 days of the upgrade.