Is this likely to be updated anytime soon to include setups where the client and server are on different machines?TV-Server/Configuration/Plugins/PowerScheduler - MediaPortal Wiki Documentation
That and the PowerScheduler Client plugin that MP has will control things well.
Now the bad news, Vista atm no mouse\keyboard activity is noticed, so unless you have a program open that is in your "exceptions" list of programs to disable the Powerscheduler, then your system will shut down after your pre-determined timeout, and immediately when you shut down your exception program.
Any mouse\keyboard activity with XP will automatically reset the standby countdown, so no shutdown occurs whilst using.