Event Viewer is a built-in diagnostic tool in Windows that logs every event occurring on a PC, helping users troubleshoot performance issues. It categorizes logs into Application, System, Security, and Setup sections, allowing users to focus on relevant categories during troubleshooting. Events are classified as Critical, Error, Warning, and Information, with Critical events indicating potential sources of system crashes. Users can filter logs, research Event IDs, and utilize the Details section for deeper insights. Event Viewer can be paired with Reliability Monitor for a visual overview of system stability. Many third-party diagnostic tools also rely on data from Event Viewer, making it a valuable resource for addressing persistent errors.