Dell laptop screen doesn't go completely off when using 'projector only' mode

Running Win 7 64
Plugable USB 2.0 Universal Laptop Docking Station with DisplayLink DVI/VGA up to 1920×1080, Audio, Ethernet, and 4 Available High-Speed USB 2.0 Ports
Dell Vostro 3300

Hi Peter,

Thanks for posting here! What you are describing is expected behavior.

When you plug in an external monitor through the video output port of your laptop, both the laptop monitor and the video output port share the same Video card and the drivers. So when you configure Windows to display only on the monitor, the laptop screen turns off because the output is going to the other monitor through the same card. In other words, the primary video card is on, but is outputting through the video out port.

When you have an external monitor connected through USB Graphics and you configure Windows to only display on that monitor, the primary video card still stays on. Since no external monitor is connected through the video output port of the primary graphics card, the laptop screen stays on (even though Windows is not sending any display to that screen).

Hence the laptop screen would be black but the screen would be lit. You would see this same behavior in ‘projector only’ mode when connecting to an external monitor through USB.

Hope the above information helps in understanding this behavior! Do feel free to post back here or shoot us an email at if you need any additional information or help regarding any of our products. We are here to help!