HP laptop powers on but stays on a black screen

Had one do this and a hard reset sorted it. Unplug the charger and anything in the USB ports, hold the power button for about 15 seconds, then plug back in and power on. If it's still black, look at the caps lock or num lock light while it's on. If it blinks in a repeating pattern, that's HP's way of telling you which part has failed (count the blinks, the pattern is in the support docs for your model). No blinking? Try Windows key + Ctrl + Shift + B, which restarts the graphics driver, or plug in an external monitor. If the picture shows up there, it's the laptop's screen or its cable, not the computer itself.