|"Dell PC" tells us only that it can run Windows. |
What model is your computer?
If your video adapter can support two displays - two monitors, or one monitor and TV out (composite video or S-Video) it's normal for you to see two display icons in Display Properties - Settings in Windows, and if one of the two is not connected, for "Not Active" to be displayed when you hold your mouse cursor over it.
If this is a desktop computer, if you have a monitor with both a VGA and a DVI input , DO NOT connect both of them to the video ports on the computer ! Only one of the two - VGA or DVI - can display at a time.
If this is a laptop or netbook, if you have an external monitor connected to the video port, things can go wrong such that you have no display on the built in display, yet Windows still detects it as the Primary display. In that case, .the two display icons in Display Properties - Settings in Windows will both NOT display "Not Active" when you hold the cursor over the icon.
RIGHT click on the display you are getting no video from and Disable it.
There is probably a key combo that toggles the display - built in display only, or external display only, or both. See the User's or Owner's manual.