Instructions
Open the map in the "Warcraft III World Editor." To open the map, click the "Open" option from the "File" menu on the top toolbar. A standard Windows Explorer window will appear allowing you to choose your map.
Click the "Map Options" settings from the "Scenario" menu on the top toolbar. A small window will appear with the "Options" tab activated.
Click the check-box beside "Hide mini-map in preview screens" to check the box and remove the mini-map from the preview screen. This will prevent players from seeing it before they are in the actual game.