Is that area blacked out during the BIOS when the computer is booting up or
are there times when it is not blacked out? If it is always blacked out, it
is probably hardware. If it is not always blacked out, could you explain
exactly when it is and isn't?
Have you tried booting into Safe Mode and seeing if it is there? This can
also happen if you ask for a resolution that your video card/monitor can't
support correctly.