While you are looking for a "free download full version," it is important to distinguish between legal "abandonware" and piracy:

Tom Clancy's , released in 1999, is the acclaimed sequel to the original Rainbow Six . It is a tactical first-person shooter that emphasizes planning, realism, and precision over "run-and-gun" gameplay. Game Overview

: Players command the elite counter-terrorism unit, RAINBOW. Missions involve hostage rescues, bomb defusals, and surgical strikes against global terrorists.