The reason I want to do this is most of the time I have the computer plugged into a 52" LCD in another room displaying information. Occasionally I need to update the software and to do so I need to see what I am doing so I plug a monitor in locally.
Problem is that it automatically adopts the device capabilities of the new monitor and thus changing the settings for the large screen. I then have to go to a networked administration panel for the software to update the resolution settings.
you don't want to disable Plug and Play, you want to disable the Display Data Channel (DDC)
On Microsoft Windows (Windows XP and newer), there is no software provided option to disable plug and play monitor detection. This causes problems with computer/monitor switching applications and causes computer games to select display resolutions higher than the monitor is physically capable of displaying resulting in a garbled display.
In these circumstances, it may be necessary to remove pin 12 from the monitor VGA cable, to disable plug and play monitor detection. This allows display resolution to be selected manually and not overridden when the display adapter is removed and reinserted or the KVM switch is operated.
the Pin # of course is different with HDMI or DVI connectors.
According to this TechNet article Plug and Play
Ability to disable: Plug and Play cannot be disabled, because system instability would result.
(I am assuming that is what you mean by "PNP").
Just open up your Services window (Control Panel -> Administrative Tools -> Services) and stop 'Universal Plug and Play Device Host' and 'SSDP Discovery Service'. Also set their start-up type to Disabled.
