distorted sound

I am running Windows XP Prof SP2,P4,512 of RAM.I used to play music while
using my computer,just lately I noticed that whenever I open another program
my sound is distorted specially when that program I opened is starting and
back to normal when the program is fully open.Again this will happen every
time I open another program.I'm using creative 5.1 soundcard.As of now this
is my only problem.How can I correct this.