"Halo: Combat Evolved" and its sequel, "Halo 2," have achieved phenomenal success on the Xbox video game platform as gamers around the world follow the saga of Master Chief in his battle against the Covenant forces. In 2003, the original "Halo" roared onto Windows PCs. In "Halo 2" for Windows Vista, the action picks up where the first game ended. Master Chief, with the help of a small group of marines, has destroyed the religious artefact and artificial world known as "Halo," and is making his way back to Earth. There, he and the last surviving Earth forces will mount a titanic struggle against the marauding Covenant enemy. To date, the Halo franchise has sold more than 14.5 million games worldwide with over 600 million hours of multiplayer action logged across Microsoft's Xbox Live online gaming service.