(posted: 1/2/2008 8:49:05 AM) Answer Courtesy of UltimateDoomsdayGame:
To delete Action Replay codes and/or reset it to Factory Settings, follow these steps!
1. Enter the Code Manager.
2. Hook up your Action Replay
3. Turn your DS on.
4. Your AR will now try to update itself. But, it won't.
5. Look in the Nintendo DS box
6: Click on every game and press the garbage can icon.
If that's too hard for you, try this.
1. Open the Code Manager
2. Press 'Quick Update'
3. Your AR will now start deleting games.
4. As soon as the process is done, turn off the connection.
WARNING: Unplugging your AR during the 'Quick Update' process might ruin your AR. Just turn it off to avoid corruption.
There. Your entire AR will be wiped out.