The official version of Halo 3 on PC is part of (MCC).
This version is strictly multiplayer-focused and does not include the official Halo 3 campaign. PC Setup & System Requirements Halo 3 Free Download PC Setup
Includes full keyboard and mouse support, FOV sliders, and a server browser for custom games. The official version of Halo 3 on PC is part of (MCC)
Before the official PC release, a community project called repurposed a cancelled free-to-play Russian game known as Halo Online . Before the official PC release, a community project
You can buy Halo 3 individually on Steam for roughly $9.99 , or even less during seasonal sales.
Finding an official "free download" for on PC is difficult because the game is primarily a paid title. While there are no legitimate, permanent free versions of the full game, there are official ways to play at low cost and community-driven alternatives. Official Ways to Play