NFSUnlimited.net

this is happening to me for the first time.when i record a video from my desktop or only audio,when i play it the sound is really crappy,its all,how can i explain,vibrating,really,really shaking!
i recorded the video and audio before but this never happend.i tried many recorders its all the same,i even reinstalled the sound card but i didnt fix anything!

help,please!?