Pop/crackles when playing music out of iTunes.

i'm having a really annoying problem. i just got a new computer (emachines amd athlon 64 3200+, etc.) and have spent the past week ripping all my cd's. however, i noticed that when i'm playing songs from my library in itunes, there are subtle pops and crackles, making it sound like a vinyl record. at first i thought it was b/c my equalizers were set too high so i lowered them. didn't help. then i switched out the crappy speakers that came with my computer for my old ones, no help. finally a friend of mine sent me an MP3 file of song, and i played it in windows media player. it sounded perfectly fine there. but when i played the same file in itunes, the same thing happened. does anyone know why the heck this is happening? i also thought it might be b/c some of the cd's i ripped were scratched, but it's happening on every single song i play, even ones from brand new cd's. hopefully someone can help me. thanks.