Used CPUOff Lite for Windows?
Developer’s Description
By JSutils
CPUOff Lite monitors average CPU load and initiates computer power off if the CPU load has been below 15% for 60 seconds. It can be started manually or automatically via the windows task scheduler. The program parameters are not configurable. The program normally runs in the system tray. Requires a registration code to run. This version is the first release on CNET Download.com.