Im not at a PC with FSX now but there is a file in the FSX basefolder called dlxkey.txt, check that one. That file could have another name if your FSX is not deluxe version, look for a file with 'key' in the filename.

• Fsx Product Key Not Working
• Microsoft Fsx Activation Key

Fsx Product Key Not Working

Microsoft Fsx Activation Key

This is the official support article from the Microsoft support website, explaining and answering questions related to the activation of your Microsoft product. This covers FSX and many other Microsoft Games and Software titles.

This article lists the frequently asked questions about how to activate Microsoft Games for Windows and Home Products titles, and about how to troubleshoot activation issues for these titles. Q1: What is Microsoft Product Activation? A1: Microsoft Product Activation tries to reduce counterfeit software, and to make sure that Microsoft customers receive the software quality that they expect. After you activate the software product, a specific product key is assigned to the computer hardware on which you installed the product. After this product key is assigned, you cannot use the same product key to activate the product on other computers. Product Activation is required to use the product in full feature mode. If you choose not to activate the product, you can use the product only in a reduced trial mode.