As the name of the thread is, i would like to know why you people flash your DS'es? What are the benefits? I owe a passcard3.
Removes the Health and Saftey screen, allows you to use things such as the Mario Kart offline course hack without having to switch the Passcard3 with the game, prevents your DS from being bricked (it installs a recovery system), some people say it saves battery life, though this hasn't been properly tested. The biggest advantage [bold]was[/bold] you didn't need a big Passkey device sticking out of the DS, but now the Passcard3 is out it is no longer an issue.
Also, if you play single cart multiplayer, a flashed DS can receive a ROM during download play whereas a normal DS can't.
An example of what I'm trying to say would be that you and your friend try to play Meteos. Your friend is starting single cart Meteos multiplayer from an M3, and you're trying to receive the download on your unmodified DS. This set-up will not work. However, if your DS has FlashMe installed, it would be able to receive Meteos and play Meteos just fine.
