I know you are joking, but a lot of different updates and maintenance chores are preconfigured to take place in the middle of the night.
For example, Windows 7 is scheduled to do a defrag of the hard drive every Wednesday night at 1:00 AM.
If you go to Control Panel, System and Security, Administrative Tools, and then Task Scheduler, you can expand the Windows node and then look at all the different default tasks and when they run, and even turn them off or change their times to better suit your needs (like for night owls, for example).
That’s your windurs update running.