Windows is not running on their servers, and the computer shown running windows seems only to be used by the techs who are putting the servers together.
Some how I doubted it (how would they QA test any of their Windows executables such as Chrome or GTalk) but it was what they announced.
Google also has a habit of releasing information to the public as if it's current, whereas it's actually what they were doing a few years previously. I wouldn't be surprised if that video segment was three or four years old.