Microsoft says Halo 2 will be available only for Windows Vista. Looks like Microsoft is jacking up all avenues to increase sales of Vista and increase revenues.

The Storyline:

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 artifact 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.

Source: XBox.com