Using a computer-based presentation system is pretty much the standard these days when it comes to any sort of teaching, training or presenting of data. While making use of a modern system certainly beats flipcharts, whiteboards and old-fashioned slides when it comes to efficiency and effectiveness, there's a chance you might develop a problem when you're about to present.
Fortunately, these problems aren't normally serious, and with a quick troubleshooting session, you can normally identify and solve the issue so you can get on with your presentation without delay.
The projector won't turn on
This is often simply a loose cable. The power cables that plug into projectors can look as though they're in properly when they're not, so make sure it's firmly inserted.
Check if the power switch on the projector is in the correct position or, if it's a button, that the light next to it is on.
If you're using an extension lead, it could be faulty, so try it without, if possible, and make sure everything on that end is plugged in correctly and switched on at the wall.
Slides are showing on the computer but not through the projector
First of all, check the VGA cable is plugged in from the computer to the projector and that nothing is loose. If this is all as it should be, the output of the computer may be set up incorrectly.
On a PC, press the Windows and P keys together and use the arrow keys to cycle through the options. If you're using a Mac, choose 'System Preferences' in the Apple menu, then 'Displays'. On the 'Arrangement' tab, choose 'Mirror Displays' and you should get it working.
Slides aren't showing up on the computer screen or the projector
Check the power and monitor lights on the computer are lit up. If so, the computer may be asleep, in a power saving mode, or displaying a blank screensaver. Try moving the mouse, pressing some keys or pushing the power button. If the computer display appears but the projector is still not working, run through the steps above.
The sound isn't working or is too quiet
Volume is normally controlled from within the computer's operating system, so check the level is high enough and that it hasn't been muted.
If you want sound through the projector itself or external speakers, the computer must be plugged in separately from the visual output.
The projection is out of focus
The projector should have a focus ring around the lens, so try turning that slowly until you get a sharp image. If it doesn't have one, or you can't find it, you may need to move the whole projector back and forth until you get a clear picture.