Nec Laptop – Hardware problem – Sigmatel sound card

I’ve got a Nec Versa E6210 and also got a problem with the sound card. when I use Media Player, Winamp or any kind of software to play mp3 file, the system will occur an error, not playing smoothly and stop all programs running. But when I plug a jack of headphone or speakers, the system run very perfectly like I wish. I tried to re-install many times the driver copied from the NEC website and find another same driver for this sound card but nothing happens! I really dun know why! So that i must use headphone to hear music all the time.
Could someone have the same problem like mine and give me a right way to slove it?