I'm afraid I cannot advice on the slowness problem, as I've always played the game in real DOS.
However, for those who feel that EA's hockey games were much better before they started using a 3D engine, I'd like to recommend downloading the Gens emulator and playing the NHL games with that. The Genesis versions of the series all used 2D engines, and especially NHL 98 plays great.
Also, you can play the Genesis version of NHL 97 for free at the
EA Sports website (choose "NHL 97 (free)" from the Hockey pull-down menu).
By the way, the Genesis version of NHL Hockey had penalty shots and the player could even control the goalkeepers. I wonder why those features didn't make it to the PC version?