How To Fix Horizontal Lines On Laptop Screen ?Black horizontal lines on a Laptop screen might be an after effect of a hardware problem or an issue with your graphic card,Here is a complete guide to troubleshoot Horizontal or Vertical Lines on Computer Screen we should do is make a correct diagnosis.If the lines aren't visible, the motherboard and video chipset are fine, and the screen is the problem.go directly to the website of the manufacturer of the graphics card.