Music Lag

I am trying to fix my parents computer that lags or stutters when playing music through itunes and windows media player. I am not looking to swtich players. Just trying to figure out why it drags. I’m not super tech savvy but I can find my way around for most things. Any idears or directions you can send me in?

3800+ AMD Athlon 64 processor
1.0GM memory
250GB Hard drive
XP OS

Thanks.