I have a setup I believe to be like the one you are describing, running a powerpoint prsentation 24/7. The powerpoint show runs on the secondary monitor and the local user works on the primary monitor. Another user remotes in to change the powerpoint presentation. Problems I encountered were:
If the local user logged off, powerpoint stopped too
If the screensaver kicks in, it blanks both monitors
To set this up, you will need an actual second video card installed in the computer you are remoting too so that you can extend your desktop. You can not simply tell Windows that the only adapter in the computer is to be treated as the secondary monitor.