Performance Monitor is a small program that shows you the CPU, Memory, Disk and Network utilization under Windows NT platforms. It's composed by four fully configurable small graphs and it can work in the tray area also.
PerfMon can become transparent and permits you to forward left-mouse clicks so you can place it anywhere. You can also change the program priority (saving CPU work) and its size (for big monitor resolutions ;-))
Right-click for options
Drag a single panel to move it
Drag a single panel with the CTRL Key down to move all attached panels