Xna - Skinned animation problem!

the prblem is that I copy the skinned Model sample of Microsoft and apply it on my own way " During to class arrangment " , then when I finish and run the program the class did not move at all , I rewrite the code again and still the same , I think may be my hardware is so fast !!!! I multiply the time by 35.0f :

        public void Update(GameTime gameTime)
        {
            Matrix world = Matrix.CreateScale(Scale) * Matrix.CreateFromYawPitchRoll(Rotat                 ion.Y, Rotation.X, Rotation.Z)
                * Matrix.CreateTranslation(Position);

            TimeSpan elapsedTime = TimeSpan.FromSeconds(gameTime.ElapsedGameTime.TotalSeco                  nds * 35.0f);

            Player.Update(elapsedTime, world);
        }

Now it's move but not forward , but backward ???????? so I am conufsed why this happen and why when I multiply the timer then Model animated?