Sound keeps on skipping and cracking

I thought at first it was just my external speakers but I unplugged them and it does it from my laptop speakers as well. It's been happening for a few days now and it's really bugging me! Is it my sound card or my speakers or something else? I've done Norton and Adaware searches just to see if that helped anything but nope. It's also been slowing down my Firefox lately. Any help would be greatly appreciated!

 

anyone? I just did the windows sound troubleshooter and none of that helped. By the way I have a Gateway Laptop w/ Windows XP