Acer aspire 5733 keyboard and touchpad got frozen

Hello,
my acer aspire 5733 keyboard and touchpad got frozen. I formated the computer and installed windows 8.1. The situation did not improve. I connected an external usb mouse and keyboard, they worked at once. Eventually, the external keyboard also is refusing to work, but external mouse is still working. How may I solve this problem? I tried to press Fn + F6, nothing happened, I tried Fn + F7 still nothing happened, then waho should I do??