Unwelcome monitor bug - how to remove it?

All of a sudden the bottom third of my monitor screen presents a simulation of a cracked gl. I am unable to remove it, even unplugging the monitor from the computer and rebooting. I thought it might be a virus so I ran a scan. Nothing. Norton finds no virus. The bottom forth of the monitor still has this gray-white bar with a black corner where it looks like a stone hit a gl monitor (mine is a flat LCD screen) cracking it. How do I remove this thing? I am unable to see the desktop below this unwelcome overlapping screen, so I cannot see or click on START or its options, or see the task bar at the bottom, etc. I followed someone's advice and tried finding a strange program running in TASK MANAGER (found nothing) and booting in SAFE MODE to see if the simulation disappeared. The cracked gl remains on the monitor -- even while rebooting! It only disappears from monitor during the 3-4 seconds the power is cut to monitor during rebooting, then reappears and remains there no matter what I do with the computer. Can't even put the cursor on the affected area of the monitor; the cursor disappears beneath it. It would seem the bug resides in the monitor -- which to me sounds crazy, but that's what it appears since it remains there even when system shuts down. Please advice. Thanks.