If you are looking for the "full game" experience with modern improvements, fans have created standalone installers that simplify the setup on modern Windows systems:
A massive overhaul that adds new songs, characters, and menus, available for both PC and PS3 (via emulator) . 2. Modern Alternatives Guitar Hero III: Legends of Rock Free Full Game...
This is the most popular modern successor. You can download the engine for free at clonehero.net and then add "song packs" that contain the entire Guitar Hero III setlist. If you are looking for the "full game"
The community has largely moved toward open-source engines that are and support all songs from the original Guitar Hero series: You can download the engine for free at clonehero
While there is no official "free" version of Guitar Hero III: Legends of Rock from Activision, you can access the game or its content through several safe, community-driven methods for PC.
Because the game is no longer sold digitally, it is often categorized as "abandonware."
A massive mod for the World Tour PC port that allows you to import the entire GH3 setlist and play with improved graphics and features. 3. Legacy Downloads