FileMonitor is a free tool that monitors and displays all the file activity on your PC. It is more than a process monitor or event viewer, it displays all running processes and activities, including those that run in the background. FileMonitor can show you when a program opens a file or initiates a process which can be useful information if it's something you haven't authorized, such as a virus. It can also tell you what's going on in the system, such as when the disk is busy; FileMonitor can identify what's writing to it. Its extensive log view lets you go back and see when a file was deleted or changed, where it's kept, and other useful information. This utility can be downloaded from here.