Windows Firewall will often activate itself if Security Center finds no other firewall present, or if the resident firewall has been switched off, but Security Center itself can be a bit flaky, as on one or two occasions, it hasn't seen my security suite, but picks it up after a reboot.
Not sure about Windows Updates, but I would have thought once set to 'Notify', that wouldn't change by itself. One way to immediately remove a Windows Update, might be to do a System Restore, but personally, I think that the general concern over WUs is a little unwarranted, as they are mainly security fixes which are needed for your computer, and usually install without any problems.