I loved that game as a kid and was almost perfected in it. Not that it was hard at all but still...the point is I could get very far without any frustration.
I really felt sad when I didnt get the duck and dog looked so dissappointed lol.
If you're interested in playing look on google for a few emulators or something. Here's a browser based one.
http://gprime.net/game.php/duckhunt doesn't work too well for me...it lags.