This is a weird situation, I'm sure, but I always seem to (or want to) do things differently than other people, and often outside the box.
I have a 4 monitor system (2 ATI video cards, dual ports). I fully utilize 3 of them on my main desk. The 4th monitor is on the other side of my desk - this is where I have visitors look at the information I'm showing them. This way they don't have to be overwhelmed by the couple of dozen things I have going on at my other monitors. So, in Screen Resolution, I have monitors 3 and 4 shared (Duplicate desktop on 3 and 4).
This works great - exactly what I want it to do. I throw things to monitor #3 and can work on it on my main desk and when I want to show stuff to visitors, I turn monitor #4 on and they can watch that one while I do stuff on #3.
My problem is that I want to leave this monitor powered off when I'm not showing stuff to visitors, and for windows to remember this setting when I reboot without the monitor having to be ON during the bootup. Presently, when I reboot with monitor #4 turned off, Windows assumes that I don't have it anymore and reassigns things (last time it decided to share monitor 2 and 3 together).
I'd even be fine with having a mode where I can enable/disable the monitor quickly with something in the system tray. Something that puts the monitor to sleep, but when it wakes up it is automatically showing what it is suppose to.