The product key for "Halo: Combat Evolved" is a unique alphanumeric code that is input when the game is installed. Product keys, which are required to unlock some games, are an anti-piracy measure. A product key is only needed for the Windows and OS X versions of the game.
"Halo: Combat Evolved" is a first-person shooter video game with a science fiction setting. It was first released on the Xbox console in 2001. The game sold more than 5 million copies by 2005, making it one of the most popular Xbox games ever. The Windows and OS X versions of the game were released in 2003.