Microsoft Visual Studio 2017 C++ Redistributables allows people to run software that was compiled for Windows using the Microsoft 2017 C++ compiler. You will need to download and install the 64-bit redistributables to run GMM. This only has to happen once, when you first install GMM on a computer. IF YOU EXPERIENCE AN ERROR ABOUT A MISSING FILE SUCH AS MSVCR120.DLL WHEN STARTING GMM, THE MOST LIKELY CAUSE IS THE MICROSOFT REDISTRIBUTABLES ARE NOT INSTALLED. The redistributables are free for anyone to install, and may be downloaded directly from Microsoft at this location: https://support.microsoft.com/en-ca/help/2977003/the-latest-supported-visual-c-downloads The MD5 checksum for the 64-bit redistributables are as follows: a57667e57017d7714af565f8a605520b vcredist_vs2017_x64.exe Download and install the redistributables directly from Microsoft (e.g., see the URL above), or from the cached version on the C Code Run web site. Stephane Charette 2018-Sep-23