Although not free, GOG offers a range of classic games, sometimes including titles from the early 2000s, with no DRM (Digital Rights Management), making them easy to download and play on modern systems.
: The best place to start is the official website of the game or its publisher, if available. Sometimes, classic games are re-released or made available for download directly from these sources.
Notably, the game does not feature a mid-mission save system, meaning any mistake can force you to restart the entire level. Project I.G.I. 1 Zip File Download Link
host individual setup files for the game. Note that these often use their own "Safe Downloader" wrappers which may include additional software. Technical Specifications & Installation