When I connect an external display to my computer, [Default Monitor] that was displayed in the [Monitor] item of [Device Manager] disappears and the registered name of the connected monitor appears twice. In addition, the screen area and the setting of colors in the [Settings] tab on [Display Properties] changes to the default values of the external display. Why is that so?
This symptom is due to the specification of your computer. It occurs because the video chip installed to your machine supports dual display as its standard function. Even though 2 monitors are displayed on [Device Manager], your computer works normally. Therefore, please use the computer as it is.
If you connect an external display with resolution less than XGA without making the dual display settings (not selecting the [Extend my Windows desktop onto this monitor] checkbox in the [Settings] tab on [Display Properties]), the screen area of the LCD may become small sometimes in comparison with that of the external display.