Inside the main directory, open the folder named PC .
Look for a configuration file related to mission progress.
Released in 2000, remains a tactical shooter classic known for its unforgiving difficulty and lack of an in-game save system. If you're stuck on a particularly brutal mission like "Eagle's Nest" or simply want to revisit your favorite levels without playing through the entire campaign, unlocking all missions is a popular shortcut.
If the cheat code fails due to your specific game version (such as certain GOG or Steam wrappers), you can manually "tell" the game that all missions are completed by editing a configuration file.