Try reinstalling the touch pad drivers and restarting the device. If that does not work there could be a problem with the cable connecting the touch pad to the main board. Did you drop it or hit it hard lately?
The backlight might be off or broken get a flashlight and shine it on the screen at an angle. If it is just the backlight then you will be able to see it one with the flash light. If you do not see anything it is the monitor or video card. You can then try using an external monitor to see if it is the screen or video card.