Lately i have being getting horizantal lines across my screen. 1st i thought it was a stuck pixel so i used a software called UDpixel to fix it but not happened so i thought it was a virus so did liveupdate and scanned with norton. I tried to take a photo of the horizantal line with a screen capturing software but when i looked at the photo it was perfectly fine. The horizontal lines looks those lines when you try to highlight an icon but its flashing and are different colours. Only yesterday was there only two horizontal lines on my screen but now there is four! Althought i am not sure isactly what this is i think it is a virus.

Try connecting another monitor. "So won’t you give this man his wings What a shame To have to beg you to see We’re not all the same What a shame" - Shinedown

ya this sounds less like a virus, and more like a problem with a) your monitor, b) your video card, or c) your video driver.