Open Addit Pro. Look at the top menu bar and click on Help or About . From the dropdown menu, select Register , Enter Key , or Unlock Full Version .

: Since the product is largely considered "abandonware" due to the lack of developer support, many users in flight simulation communities recommend utilizing built-in FSX tools or other modern freeware managers that do not require legacy registration keys.

If you have a .edu email address, contact the developer directly. Many scientific software tools offer 50-80% discounts for students, and sometimes free licenses for instructors.