huh? Is the screen totally blank? If so, just put in a new battery...If the dead battery sign just went away and you can still see the tamagotchi, the battery probably has a bit of power left, but it would still be best to replace it.
it jus means da battery has gone completely, u can stil press download wen u changed it. happened 2 me loads of times b4 wen i couldnt find anywhere dat sold da rite size batteries.