Instructions
Delete Game File
Power on your Gameboy Advance with the Pokemon Emerald cartridge inserted. Wait for the "Press Start" screen to load.
Press "Up" on the directional pad. Leave the "Up" button depressed.
Press the "Select" button, while still holding the "Up" button. Leave both buttons depressed.
Press the "B" button while the "Up" and "Select" buttons are still depressed.
Choose "Yes" when "Clear All Save Data Areas?" appears. The game save file will then be removed.
Override Saved Game File
Power on your Gameboy Advance with the Pokemon Emerald cartridge inserted. Wait for the "Press Start" screen to load.
Press "Start" to make the saved game file or files appear.
Click "New Game." This will allow you to begin playing a new game of "Pokemon Emerald."
Play the game until you are ready to stop and save it and then press "Select."
Choose a game file to override when prompted to do so. The game will say "Saving" at this point and may take a few moments to override the old file and save the new one. Do not power off the Gameboy Advance or press any buttons during this time. The game will return to the home screen once the save and override is complete.