If you absolutely must play Project I.G.I. 1 on Windows 10, use a trusted abandonware source + a VM (VirtualBox with Windows XP) — that’s the safest way to isolate the game from your main OS.
Since the game is no longer available on official storefronts like Steam or Epic Games, users typically rely on legacy archives and third-party download sites: Internet Archive project igi 1 download for windows 10