There are a set of Power related API's (http://msdn2.microsoft.com/en-us/lib...9(VS.85).aspx). I've not studied them in depth, but it looks as if you can dynamically change the current Power Policy, however looking at the structures involved, it seems that you can only power down all the spindles rather than select a particular device. (But ,as I said, I've only had a quick look)