Windows 7: audio chopped/lagging

I am having a problem in sound which is due to nvidia 9400GT,,,actually the problem is that whenever iam listening on WMP or watching videos on VLC or any other utility/app the sound get chopped/lags as i refresh the explorer or the desktop,which is quite annoying!firstly i ignored it i thought it will rectified,,but the problem remain as of now.So i uninstall the Graphic driver(NVidia 9400GT),,and then tested the sound,it played surprisingly,but then i cant use my graphic,,,then i reinstalled intel chipset G31 drivers,audio(realtek HD manager) and lastly nvidia drivers,and after restarting i check the sound and it reamains the same!!



one thing to mention i was earlier using XP3 there was never a problem of this kind,so that means my hardware is quite ok as it seems to,,

my system specs-platform intel core 2 duo E7500/G31+ICH7)
Memory-3GB DDr2
Storage-500GB
display adapter-Nvidia 9400GT
windows ultimate 32 bit