I don't think this problem is related to a virus, most likely this is a hardware relate issue.
Here are some troubleshooting tips.
Test your laptop with an external monitor attached to the VGA port. If the external video is working fine then most likely there is nothing wrong with the motherboard or video card and the problem is somewhere inside the laptop display panel. Most likely you have a bad LCD screen.
I doubt that this problem is related to the video cable because when you have a bad video cable it affects video on the whole screen, not just on the part of the screen.
I guess you'll have to replace the laptop screen.