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Quite often a dvd wont play on screen if there are two outputs selected. So if it works on the laptop without the projector connected, then when you connect the projector change it to output to just the projector (CRT on your laptop)

Try rebooting your laptop, with the projector already connected and turned on. That way your laptop will automatically detect the projector.
Otherwise you need to go into your display settings (control Panel) and enable the projector.

Try lowering the resolution on your computer. Some projectors cannot handle the higher resolution when playing a movie.

You need to give us the message that the display gives you. Just saying “It says something about ‘display settings’ ” does not help us at all.
Exact wording is very important in troubleshooting error messages.
Now, read the directions and find out what resolution the Projector needs to be set to, and make sure your DVD playing software does not change that during playback.

Most projectors will play video files fine at 1024×768 32 bit resolution – perhaps even higher. The resolution your projector can handle is more on the projector than it is on your laptop.
Start the laptop up connected to the projector. (Hook it up and power it on while the laptop is powered off)
Right Click on your Windows wallapaper somewhere and hit properties from the menu that appears.
A window will appear. Click on the settings tab.
Change your resolution to 1024×768 at 32bit color, and hit OK.
See if you can play DVDs at that resolution.
If it doesn’t look good – try taking the resolution up a notch, and then another notch. The more pixels – the prettier the picture.
IS IT DISPLAYING ANYTHING ON THE PROJECTOR – OR JUST NOT PLAYING DVDS. YOU NEED TO TOGGLE THE DISPLAY ON YOUR LAPTOP *USUALLY A FN KEY + ONE OF THE F KEYS* TO DISPLAY ON THE PROJECTOR
Best of luck.