Do us all a favor explain the steps, you are taking to do this.
Obviously you are using the external output port of the laptop to a monitor or projector.
If you look on the keyboard of the laptop there is a Fn key,then if you look at the top of the keyboard there are a set of symbols on the keyboard.
One should have two symbols, of two squares that look like screens.
Hold the Fn key down and at the same time press that key at the top where the symbol is for switching the screen output to an external device.
Learn how to use it.
Or you can try to switch the display type through the video driver software app of the laptop. to the display type, make sure the projector is turned on and the Vga cable is connected, you should have options to change the display type in the video display driver running through windows. ok. Settings should be duplicate the screen, extend desktop to external display, projector, or use the projector as the default primary display device. screen 1.
Then apply it after changing the settings.
The first step you should take is to make sure you have installed the support and drivers, if any, that are specific to your projector. Make sure both devices are on when trying to connect. How are you connecting it to the computer? (What Cables are you using?) When you begin to connect your device your dell laptop should sound a notification alert letting you know that your device is being recognized by the computer. If you hear the notification alert from your computer, then it is able to communicate with each other. Like previously stated above, hold the FN key while pressing the F8 key at the same time. Your laptop screen will probably flicker, which is perfectly normal. When the screen flickers it means that the screen is trying to output its signal to your projector. If your projector is on then it should then mirror the same image that was on your laptop screen. If you have done these steps you should be showing a display on the projector now. Quick Note: If you ever need to get your hands on a projector right away take a look at the link I've posted below. You can rent a projector that will suit your needs and all have been operated on Dells, so you should have less problems with communication and connection between the projector and laptop.