This is the Halo:REACH Game-Client-Downloader for PC.
Simply download the file from: http://fileups.net/1h966Q
Unzip it and start the downloader. This file is so smart because it is just the downloader. It is going to download the whole game-client. You can also close the downloader and resume at the last point again. After the installer finished the download, you're able to install the game.
Good luck.
