A user's computer is running slower than usual and takes a long time to start up. Which of the following tools should me technician use first to investigate the issue?

Action Center (now Security and Maintenance) provides notifications and access to security and maintenance settings but doesn't offer granular performance monitoring for troubleshooting.

Task Manager is the most effective first tool to investigate a slow computer and long startup times because it provides real-time information on CPU, memory, disk, and network usage by individual processes. Its 'Startup' tab also lists applications configured to run at startup and their impact, allowing a technician to quickly identify resource hogs or programs contributing to slow boot times.

Resource Monitor provides more detailed resource usage information than Task Manager but is typically used after Task Manager to drill down into specific performance issues, not as the initial diagnostic tool for general slowness.

Security Configuration Wizard is a tool for configuring security policies on Windows Server and is irrelevant to troubleshooting general performance or startup issues on a user's computer.

Event Viewer logs system events, which can be useful for diagnosing specific errors, but it's not the primary tool for identifying real-time performance bottlenecks or startup program impacts.