HAC2/Installation
The installer can be downloaded here: HAC2_loader_install.exe
MD5SUM: a543fb7a59d54054a23aa50f57d48e93 SHA-1: 259379b745ecb0aa6faaf7e4d7af8d0a1642a7bd
This is build #3 of loader.dll - if there is an update available, and you're running a newer version of HAC2, once you run Halo it will ask you to press F1 to install the loader update.
All files downloaded by loader are SHA512 signed using a 4096-bit RSA key. Once you have a legitimate loader installed, it would be impossible for a rogue web site to hijack hac.dll, the loader updater, or any other supporting files.
PLEASE NOTE: The original loader would download hac.dll to the user's TEMP folder. Version 2.0 of the loader now downloads everything into your Documents\My Games\HAC2 folder. For Windows XP and later, press your Windows key, and click Documents. From there, navigate to My Games\HAC2. You will find a HAC2.ini file, and a Downloads folder that contains all files downloaded by loader, including hac.dll
Detailed instructions:
Run the installer.
You will see this:
Make sure Halo is closed. Click Next.