From the beginning, you know the end. And it ain't pretty. Ten years ago Halo bounced onto the original XBox. Within weeks, that game alone had sold millions of copies, saved Microsoft's white elephant from the scrapheap and launched a brand which has gone from strength to strength, spawning two sequels, a real-time-strategy title, add-on packs, animated films, books, posters and... soap. Halo is a powerhouse.