Here's the best explaination I've found so far:
QUOTE
The while lines at the top of the screen carry data. Line 20 is generally the closed captioning data stream, where your television is getting the words to decode and display on your screen.
Further above that is generally time code data and sync information from the master video file.
A short excerpt from Wikipedia:
Vertical Interval Reference
The standard NTSC video image contains some lines (lines 1–21 of each field) which are not visible (this is known as the Vertical Blanking Interval, or VBI); all are beyond the edge of the viewable image, but only lines 1–9 are used for the vertical-sync and equalizing pulses. The remaining lines were deliberately blanked in the original NTSC specification to provide time for the electron beam in CRT-based screens to return to the top of the display.
END QUOTE
Unfortuantely, no details on how to remove this. I'll look at my video card settigns and see if I can get overscan setup.
BTW, it seems to only appear on SD material (4:3 on my 16:9 screen).