When building on Windows, external dependencies should be placed in this folder. C++ headers go in the 'include' folder, as shown in the file tree below. Libraries go in the 'lib' folder, without any subfolders. This should be the resulting directory structure: Externals | readme.txt (this file) | +---include/ | +---zconf.h | +---zlib.h | | | +---curl/ | | \---(All curl headers) | | | +---GL/ | | \---(All GL headers) | | | \---SDL2/ | \---(All SD2L headers) | \---lib/ (All libs here) You may not need to hunt and compile the headers and libraries all by yourself: * There are pre-compiled zip files containing all required files for some versions of Visual Studio * They're already packed in the correct layout. You just need to merge. Visual Studio 2010: https://dl.dropboxusercontent.com/u/37804131/OpenSpades-Externals-Windows.zip Visual Studio 2015: https://www.dropbox.com/s/pfvk8tns1qgkxpr/OpenSpades-Externals-Windows-VS2015.rar?dl=1