- Python 2.7.x should be installed, and available in path. To verify, click start, run, type python and it should open it). If not, download from https://python.org/downloads/.
- FFMPEG must be installed properly, instructions are on http://adaptivesamples.com/how-to-install-ffmpeg-on-windows/
- If you have Visual Studio 2013 or 2015, make sure C++ Build Tools are installed. Simply create a new Empty C++ project. If prompted to install the C++ files, do so.
- Alternatively, you can install only the Visual C++ Build Tools as a standalone: http://landinghub.visualstudio.com/visual-cpp-build-tools
- Some users have reported that installing VLC helps with codec dependencies, so try that.

Run the following commands to re-install discord.js

npm cache clean (to remove any cached versions of discord or its dependencies)
npm install -g npm (this will update NPM, and fixed it for some users!)
npm install --save --msvs_version=2015 discord.js (change version to 2013 if using VS2013)

If any errors show, attempt to re-install node-opus manually:

npm cache clean
npm install node-opus