Your audio is skipping because your processor is a little slow. The rest of your computer is absolutely fine, so a processor upgrade will solve the problem. Just make sure it is above 1.2GHz to see a big improvement.
N64 emulation is more CPU intensive, so your gfx card may be able to handle any PC game, but it has a more minor role in N64 emulation.
In the meantime, you can try using another sound plugin such as Azimer's 0.30/0.40 and syncing the game to audio in the audio plugin settings.