Windows boxes on Ethernet LANs are now in control of the UK's nuclear-propelled and nuclear-armed warship fleet.
http://www.theregister.co.uk/2008/12/16/windows_for_submarines_rollout/
All jokes aside, even the best configured Windows PC's fall over every now and then, really wouldn't want that happening at an important time.
The US navy tried to use windows to control a battleship once (USS Yorktown) and it ended up dead in the water when the network crashed and took out the engines.



