In order to move your already registered FileFlow Server to another computer, please first make sure that you have a transferable license based on the description of How do I know if I have transferable license?
To move the already registered FileFlow Server to another computer, uninstall the product from Control Panel on the computer to free up your license for use on a new computer.
When the uninstallation is complete, install the FileFlow Server on the new computer and register with your existing serial number.