I am using subsonic on a windows PC with XP SP3.
I have configured this PC to change into hibernate after a specified time of idleness. When this PC is needed you can wake it with a Wake on LAN magic packet.
Windows resets its system idle timeout only with real user activity by mouse or keyboard. Apllications that need to stay active as long as there is network activity for instance have to care for themself and tell windows, to stay alive.
Therefore it is necessary to enable subsonic to care in this way and I think it is not difficult to to impliment this.
Microsoft describes the know how to handle with that:
http://msdn.microsoft.com/en-us/library ... 85%29.aspx
http://msdn.microsoft.com/en-us/library ... 85%29.aspx
Subsonic should reset the idle timer with login and than keep the system alive with continuous resets as long as there is network traffic going on.