Why Windows Automatic Update Doesn't Interrupt Important Transfers

One of the excuses some people use as to why they don't use Window's automatic update service, is that it will eat all their bandwidth when they are playing multiplayer or doing something else like watching streaming media and just be annoying, but Windows Update uses Microsoft's BITS (Background Intelligent Transfer Service) program. So it only uses the bandwidth that isn't being used.

So when somebody (usually Microsoft people) says there is no reason why anybody should not have auto update on, they really do mean it.