When I said “Windows” I did not mean the ones that we open to breath some fresh air (or water in the case of submarines!).
The Royal Navy has begun using a modified version of Windows XP on their nuclear submarines. And about security (since these are nuclear submarines), they have mentioned that all hack-prone elements of Windows XP were fixed during the modification (wonder if anyone can buy this Windows For Nuclear Submarines!)
Take a look at this modified version of the Bliss wallpaper in flickr. It would be a perfect match for the workstations in the nuclear submarines