My first installation of the 777 resulted in a sim which did not behave properly.  Some years ago, a MS tech told me that you should always build a new fsx.cfg file everytime you install a new addon.  Another told me that corrupt dll.xml files can also cause problems.  So here is what I did, resulting in a smooth operating sim.

 

1. Uninstall the 777 using the control panel "uninstall" function (as recommended by PMDG).

 

2. Deleted the "dll.xml" file.  Usually found at: users\your name\appdata\roaming\microsoft\fsx.  You may have to "unhide" files.

 

3. Make a new "dll.xml" file by running the FSUIPC installer.

 

4. Delete the "fsx.cfg" file found in the same location as #2.  Make a note of all your preferred fsx settings (graphics, scenery, etc.), and any manual changes you made, such as HIGHMEMFIX=1.

 

5. Install the 777. This will install the aircraft and add the needed code to the "dll.xml" file.

 

6. Run fsx.  This will build a new "fsx.cfg" file.

 

7. Modify the fsx settings and "fsx.cfg" settings you noted in #4.

 

8. Fly.

 

I hope this will help some of you to solve some of your problems.

 

Bad idea to delete the dll.xml. Every addon dll has an entry there. Do you want to reinstall them all??