One of 3 thing is your problem. Battery, Starter, selonoid. (I am willing to be selonoid is bad) Check in that order too. Try jump starting mower, just like you would a car. It is starts right up then your battery is the problem. If it doesn't start, jump the starter. If nothing happens then it is the starter. If you tried both and neither did the trick, replace the selonoid. Let me know how it goes. The buzzing sound is power attempting to turn the starter but not able to.
cholbach, October 2005