check the trim on you transmitter - set it to neutral, check all the wiring in your can make sure everything is plugged it the right way so loose or damaged cables, check batteries are all ok and fully charged, then re-program the esc, if it still does it my bet you need a new esc, i cooked an old one and all it did was go fowards at full pelt - what motor are you running and what gearing are you using, if the motor doesn't have enough tourqe the current it'll pull through the esc will fry the electrics!
johnny