Event 6009 not logged from a reboot

Hi,

There is a KB Article ID: 196452 that says Event 6009 is logged during every

boot and indicates the operating system version, build number, service pack

level, and other pertinent information about the system. Depending on your

current configuration, it gives a message similar to: "Microsoft ® Windows

NT 4.0 1381 Service Pack 6 Multiprocessor free".

However, There were instances that Event 6009 is not logged even the machine

is rebooted. What could be the possible reasons this event is not recorded to

determine that the machine is rebooted?

Any help is greatly appreciated. Thanks.