How does Trent Reznor make music?

Specifically, in making Year Zero. I saw a clip on Youtube and he said he wrote some of the bits on his laptop during the With Teeth tour. What computer program does he use to create his music? Does he use a lot of keyboard sounds? How does he create the drum sounds? Etc. I'm just curious how he creates his music. Any info on this would be super duper. lol