Instructions
Place the Action Replay into the Nintendo DS and press the "Power" button. You do not have to enter your Nintendo DS game to delete the codes from the Action Replay.
Access the "Menu" to reveal the list of games that are currently on your Action Replay. Highlight the game whose codes you want to delete and press "A" to access the video game's code list.
Highlight the cheat code that you want to delete and press "A" to place a check in the box near the code.
Tap the "Trash Can" button in the upper-right corner of the bottom screen to prompt a confirmation menu. Press "A" to confirm and delete the cheat code.
Repeat Steps 2 through 4 to delete additional cheat codes.