On booting up the computer, my cat decided to jump on the desk and mash some keys in the top right of the keyboard. I know that he at least pushed the Scroll Lock key, and probably also pressed Pause/Break and Num Lock, and maybe some others. So I put him on the floor with a bit of muttering, but figured there'd be no harm done.
When I looked back at the monitor, I was horrified to see that the loading screen had a grid of small black squares all over it. When Windows loaded, the display was blitzed (as you can see in the screenshot). I figured it was just a glitch, I'd reboot and it would go away. It didn't. I shut the computer down, left it off for a minute, rebooted. Still blitzed.
I updated my graphics card driver through Windows Update, and checked all the cables were plugged in properly, but no joy.
Help!