Alright so I've had this HP laptop for a couple months a good 6 since I got it for Christmas and it's June. So I've just been getting these weird flashing lines and I'm not sure how to fix it for good. since it goes away on it's own eventually but sooner or later will most likely come back. Here is a screenshot of it! I'm not sure if it's a GPU issue and I hope it isn't, but just wanting to know! https/img00.deviantart.net/0b73/i/2018/161/4/c/screenshot__3__by_likielida-dce1hrt.png screenshot.
1. Turn the laptop off (not sleep or hibernate but off).
2. Connect an external monitor to the laptop.
3. Turn on the external monitor.
4. Turn on the laptop.
NOTE: You may have to press an "external monitor" button. Could be the f4 button or a button with two monitors on it, for the external monitor to work.
If you can see fine on the external monitor, then your attached display, or the ribbon cable that connects it, are your problem.
If you can't see on the external monitor at all, or the problem occurs on the external monitor as well, then it is probably the graphics card/GPU that is the problem, which may require the motherboard be replaced.