Power saving for desktop pcs

[WolfgangZ]

Hi,

I'm running Feisty on a AMD64 X2 3800+ machine and I want to know if it 
is possible to use some power saving mechanisms to save electricity when 
the computer is running but has nothing really to do. The only thing I 
found was the "Power Management Preferences" but there I can only put 
the computer/monitor "to sleep" after 31 minutes.

Are there other possibilities like switching off hard disks, speed 
stepping of the processor,...

Thanks for any help!
Wolfgang