You receive a "The original file (gps_export.dll) is either missing or has been changed from its original state" error message when you install the Flight Simulator 2004 Update V9.1 (894274)

SYMPTOMS

When you install the Microsoft Flight Simulator 2004 Update V9.1, you may receive the following error message:

The original file (File_name.dll) is either missing or has been changed from its original state. The update cannot continue and will now exit.

CAUSE

This issue may occur if some third-party add-in providers for Microsoft Flight Simulator have updated various files that are located in the Modules folder of your Flight Simulator installation directory, such as the Gps_export.dll file. Sometimes, these updated files can cause the Microsoft Flight Simulator 2004 Update Setup program to quit before it finishes the installation of the update. By default, the Modules folder is located in the following folder:

C:\Program Files\Microsoft Games\Flight Simulator 9\Modules

WORKAROUND

To work around this issue, re-install the files that were originally installed by Microsoft Flight Simulator 2004 - A Century of Flight. To do this, follow these steps:

Insert the Flight Simulator 2004 - A Century of Flight CD 2 into the CD or DVD drive.
Open the CD drive in Microsoft Windows Explorer.
Double-click Msgame3.cab.
Right-click the .dll file that is listed in the error message that is mentioned in the "Symptoms" section, and then click Extract.
Locate the C:\Program Files\Microsoft Games\Flight Simulator 9\Modules folder, and then click OK.
Remove the Flight Simulator 2004 - A Century of Flight CD from the drive, and then try to install the update again.

Note Third-party add-in software for Flight Simulator that was previously installed may not function as expected. Reinstalling third-party add-in software may overwrite the updated files, and you will lose significant fixes and updates included in the Flight Simulator 2004 Update V9.1.