Event Log Entries with Windows Reboots
# Event 6005 is logged at boot time noting that the Event Log service was started. It gives the message "The Event log service was started".
# Event 6006 is logged as a clean shutdown. It gives the message "The Event log service was stopped".
# Event 6008 is logged as a dirty shutdown. It gives the message "The previous system shutdown at time on date was unexpected".
# 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 R Windows NT 4.0 1381 Service Pack 6 Multiprocessor free".
via Why Windows NT Reports 6005, 6006, 6008, and 6009 Event Log Entries.