horizontal lines on my screen

Reinstall your graphics drivers and see if that fixes the problem.

Modern computer monitors, typically LCD displays, offer high-definition images and a sleek form factor. These energy-efficient screens contain liquid crystals between two sheets of polarized glass, sending electrical currents throughout the crystal molecules to create images. Couple this high-tech process with the fact that your monitor is also susceptible to software-based issues and it's little wonder that you may experience the occasional display error, including unattractive horizontal lines. When these appear, target software remedies before seeking professional assistance for hardware fixes.

Check the HDMI, DVI, VGA or any other type of cable connecting your monitor to your computer, if you're using a desktop computer connected to an external monitor. Ensure the cable is securely connected to the respective input port -- in some cases, a loose connection can cause display errors.

Download and install the most current hardware drivers for your Windows 8 operating system. Without the latest drivers, your LCD monitor may produce unwanted lines. Enter your computer's Settings menu, accessible by swiping from the right edge of the screen or hovering your mouse at the right edge, and choose “Change PC settings.”