lines suddenly appeared on screen

There are 2 vertical and 2 horizontal lines on any view on the screen. I have windows 7. They appear on the home screen, word processor documents, on the internet. It makes 9 square boxes on the screen. Does anyone know what this is? I've tried everything including rebooting.

I got it. It's the Asus monitor. There are buttons on the bottom which if accidentally pressed will cause the lines. It's unfortunate they don't somehow notify you of this since otherwise you could spend hours trying to get rid of them. I googled the problem and on a microsoft site they went through all kinds of driver settings. One reply said 'forget it', it's the monitor!

I was going to suggest the monitor, but you got it resolved before I could answer.