B777-300 for FSX 1.0 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The actual developer of the program is AeroSim Co.,Ltd. B777-300 for FSX lies within Games, more precisely Utilities. We recommend checking the downloaded files with any free antivirus. The most popular version among B777-300 for FSX users is 1.0.
From the developer:
It's an add-on for exclusive use with MS Flight Simulator X. Flight SimulatorX with SP1 (SP2 recommended) or Acceleration is required, as well as a video card with DirectX9.0c or later version.
This expansion provides the Boeing 777-300 aircraft with 2D and 3D cockpit, and a flight dynamic to have you able to immerse in the operation of B777-300
in the Microsoft Flight Simulator X.
You may want to check out more software, such as SCS Tupolev Tu-134A-3 FSX FSX-Steam, Super King Air B200 FSX / P3D or FSX Grumman E1B Tracer, which might be related to B777-300 for FSX.