>One of our customer is able to disable 'Duplicate mode' on 'second screen' option, and we wondor how to implement it, as following pic Once you've found the display device you'll need to get a valid display mode to change it to, you can find this by calling the EnumDisplaySettingsEx() API call. Use the EnumDisplayDevices() API call to enumerate the display devices on the system and look for those that don't have the DISPLAY_DEVICE_ATTACHED_TO_DESKTOP flag set (this will include any mirroring devices so not all will be physical displays.) If you want to duplicate screen to the 2nd display monitor, please consider using Device Context functions: >How do I accomplish this feature? By windows API or registry, or Windows System Image Manager(WSIM)?