One other thing to keep in mind is your monitor's refresh rate. If you have it set too low, you'll get those lines.

The refresh basically determines how long it takes to clear your screen for the next image, and if it's too low you'll see some tearing.

Make sure that your monitor is set to 60Hz, and check your computer graphics settings to make sure they're at 60Hz as well.

If this doesn't fix your issue, then you should definitely look into getting the computer checked for any hardware malfunctions/power issues.