My daughters acer one goes black after start up

Take the netbook into a dark room and see if you can see the screen. There are three possibilities here....either the screen is on and the backlight has failed or there is nothing on the screen because the inverter has failed or the screen itself has failed. If you take the netbook into a dark room and shine a flashlight on the bottom section of the screen, if you see the desktop or test etc. then the screen and inverter are good and the backlight has failed. If however you don't see anything on the screen and you are sure the laptop booted, then most likely you have lost the inverter or the screen itself.