Try Windows Key () + P Key to bring up this menu, select duplicate and see if this resolves your issue.

If this doesn't resolve your issue please check your connections (typically VGA) on the back of your computer

If that doesn't resolve your issue please check that your projector is on and that the lamp light isn't red. If this is the case or if you were unable to resolve the issue with these steps, please contact IT Support and someone will assist you.