Event Viewer can be used for checking unauthorized use of computer, viewing event logs, fixing problems & errors, and monitoring & tracking trespassers.

Aside from being an Event Viewer on steroids, Event Log Monitor provides you a single launch point for daily administrative tools. You can start the Registry Editor, Server and User Managers ...

The Windows Event Viewer is an important diagnostic tool, but even it sometimes requires troubleshooting.

Sysinternals Sysmon is a system monitor tool for Windows to monitor the health of Windows OS, using system log files. Available as a free download from Microsoft.