One of the most powerful tools for troubleshooting a PC has been built into Windows since the early days, but is still widely misunderstood. It's known as the Event Viewer. The tool itself is merely a window into a particularly useful feature of the operating system, namely that it keeps a log of just about everything it does. Every time a process starts, or you log into your PC, or just about anything else happens, a log entry is created. It's not uncommon for tens of thousands of entries to be created every week. Event Viewer lets you view and search these event logs to help track down the cause of a problem.