Does it have to be a desktop? How about a Macbook Air or some netbook with a monitor attached? Or why not just hibernate the machine he already has when sleeping?
The person is disabled, so getting to the PC just to turn it off or hibernate it is quite a hassle. Also, it needs to be able to run Windows XP or greater in order to run her software. One option I'm considering is a Mac mini running Windows via Virtual Box or VMWare or Parallels, but that seems like overkill. Seems like there should be a small quiet reasonably-fast Windows box for under $500 from someone (she already has a nice monitor, and her special keyboard and mouse). Thanks again.
Can't you just set the automatic hibernate timer to something reasonable?
It would auto wake when the keyboard/mouse is used.
So get a used Mac Mini for probably $300. Any 2009 and up models are still fairly powerful machines, and are better and quieter than any desktop PC I've owned.