Projector not showing the same as the Computer Monitor?

Sometimes a computer does not show the same image on the projector as on the monitor. This is usually the result of a cable previously having been unplugged.

For Desktop PC's:

This is quick and easy to resolve. On the Start Menu there is an icon in the ‘Utilities’ folder called ‘Duplicate Monitor & Projector Output’

This does exactly what it says, and should resolve the issue for you instantly.

For Laptops:

Pressing Windows Key + P will open the projection menu where you can choose to duplicate or extend your screen: