PLEASE NOTE
Microsoft Flight Simulator X: Steam Edition (FSX: Steam Edition) is functionally similar to the boxed version of Microsoft Flight Simulator X (MSFSX). We have worked extensively with third party developers to make sure the two products can work alongside each other, however due to the wide range of add-on products available for MSFSX, we cannot guarantee that your existing content will work with Microsoft Flight Simulator X Steam Edition.
Sounds a little fishy?