FreeMeter is
a utility that helps you keep track of your system's
resources, by monitoring, in real time, disk space
usage, CPU usage, memory usage, and disk transfer rates.
FreeMeter can be used for observing your computer's
activity or for diagnosing technical problems. You can
customize the display to show just the information
you're interested in. You also can place icons in the
system tray that depict system usage.