Each aircraft folder has an aircraft.cfg file.

In the aircraft.cfg file there are [fltsim.x] sections.  FSX treats each [fltsim.x] section as a separate aircraft.

In each [fltsim.x] section there are two lines that FSX uses to assemble the aircraft name that it will display in the aircraft selection window:

     ui_manufacturer
     ui_variation

Most likely you have a Boeing 777 airplane folder in which the aircraft.cfg file includes one or more [fltsim.x] sections that describe the bogus aircraft.  If so, then it's an easy fix.

1. Make a backup copy of the aircraft.cfg file.
2. Open the aircraft.cfg file in notepad (must use a plain-text editor).
3. Look for the bogus aircraft name.  Remember, FSX uses two separate lines to assemble the display name, so look for only part of the name (for example, 'Australia').
4. To eliminate an unwanted [fltsim.x] section, first comment out the unwanted section by inserting '// ' in front of [fltsim.x].  FSX will ignore that section when it runs.   Then run FSX to ensure you haven't introduced a new issue.  If everything is OK, then you should be safe in deleting the unwanted [fltsim.x] section from the aircraft.cfg file.

Note: Each aircraft.cfg file must have a [fltsim.0] section.  If [fltsim.0] is the section you want to delete, then rename another [fltsim.x] section to be [fltsim.0].