Please help, I've played Harry Potter and the Chamber of Secrets on PSone heaps of times and I still end up with 96%!!! Do I still have uncompleted areas in the game or is 96% the highest percentage possible? PLEASE HELP!!!

Well, I'm quite sure that I have done everything I can.... Oh wait, There is one thing I still can't beat which is the giant purple bouncing thing that's located through a secret passage that Neville Longbottom is standing outside after Herbology. You go through the wall and you end up in a little yard where there's lots of small purple bouncing things and amoungst them there's a giant one. I can destroy the little ones with a Flipendo, but everytime I hit the big one with it, it turns orange and starts jumping after to me. Usually I just keep hitting it with a Jinx, until it gains too much speed and eventually hits Harry and he loses health. Could not defeating this thing be my problem?