I did set the system to sleep if inactive for four or more hours. It hasn't availed itself of that yet. I suspect that it is because the Ethernet adapter was set to wake it up, and the server periodically makes sure that its WINS entries are up to date, and so queries all the computers it can every ten minutes or so, and this probably kept the system up. I have disabled that, and hopefully the system will go to sleep on its own. We shall see.