Why? Because it's much easier to create an invisible button and just duplicate it. It saves a lot of time. And if you ever need to change a label, you just change the text, you don't need to change a whole button. You will now make the invisible buttons.
Create a new ActionScript 1 or 2 Flash movie, set the dimensions to 620x420px, the framerate to 30, and the background colour to its default value as it does not matter. Name the only layer in the timeline Map and import the main image onto the stage and then lock the layer.