Laptop power is on but No screen ddisplay

You can try using the function keys on the keyboard to adjust the screen brightness to see if it helps. If you can see the screen properly when you shine a flashlight on it, then your backlight has failed and needs a replacement. You could also try plugging the laptop into an external display to see if it displays properly on an external monitor. If the screen only goes black after Windows loads, you can press F8 to use VGA mode and see if the screen displays properly.