An event is any significant occurrence in the system (or in an application) that requires users to be notified. Some critical events, such as a full disk drive or an interrupted power supply, are noted in an on-screen message. Those events not requiring immediate attention are noted in an event log. Event logging starts automatically each time you start Windows NT Workstation. With an event log and a tool called Event Viewer, you can troubleshoot various hardware and software problems and monitor Windows NT Workstation security events. You can also archive logs in various file formats.