In the beginning sequence, where Ash, is discussing cutting off his hand, he picks up his chainsaw, which promptly begins running. He never pulls the cord, which any rollerskating circus monkey with half a brain knows you must do to get a chainsaw going!
Also notice that he is in the the living room and not in the kitchen like in ED2. The floor doesn't have broken plates on it either. In ED2 he stabbed his hand with a knife to keep it from moving, but in AOD the knife is gone.
According to the DVD commentary on the Gold Limited Edition copy of the Movie...the reason that scene has changed was because Sam Raimi felt the original scene did not pace as well for a prologue and was re-shot for the AOD intro. Hope that helps :)