Well, maybe the next thing to look at is the file format for NES ROMs:
http://wiki.nesdev.com/w/index.php/INESThere is a separate memory space for graphics, on the NES. The Donkey Kong cartridge has two ROMs in it, not just one. One is called the PRG-ROM (used by the CPU), and the other is called the CHR-ROM (used by the PPU graphics chip).
The PPU memory layout is described here:
http://wiki.nesdev.com/w/index.php/PPU_memory_map$0000-$1FFF on the PPU is mapped to the CHR-ROM in the cartridge. It represents the graphics tiles used for sprites and backgrounds. Does this explain the extra $2000 worth of data you found?
DarkMoe wrote:
I searched the rom for "9E C7" with a hex editor and couldn't find it. So where is it supposed to be?
You'd expect it to appear at $FFFC when mapped into the CPU's memory space. You've already realized that Donkey Kong only has 16k, and not a full 32k, so it gets mirrored at both $8000 and $C000. $FFFC is in that second region, so the offset of the reset vector in the ROM is:
$FFFC - $C000 = $3FFC
Finally, an iNES file has a 16 byte header, so:
$3FFC + $10 = $400C
That's where you should find your reset vector ($9E, $C7).