Restart the laptop
Check if the lines appear in BIOS or startup screen
Connect an external monitor
Update or reinstall the display driver
Run Windows Update
Adjust screen resolution and refresh rate
Disable and re-enable the display adapter in Device Manager
Perform an HP hardware diagnostics test
Check for loose or damaged display cable
Inspect the screen for physical damage
Reseat the RAM
Boot into Safe Mode
Restore the system to a previous point
Reset the BIOS to default settings
Update the BIOS
Replace the LCD screen if the problem remains
Contact HP support or a repair technician