Vista - Help me!!

Hi Friends!
I Have a strange problem and need your help.
Recently I bought my new machine with the following configuration :-

MSI P7N2 Diamond Nvidia 790i ULTRA SLI chipset motherboard
Geforce 9800 GTX+ 512 MB (Plait)
2 GB DDR3 RAM
Intel Quad Core 2 Processor

I installed Windows Vista Ultimate x64 in it and installed all the latest windows updates available on the internet using windows update service.

Everything works fine, but while working the sound cuts off automatically, and comes back when i restart the particular application(example: Games,Windows Media Player while listening to songs, watching movies or anything else).
Then after few seconds or minutes (depends on its mood) it cuts off again and the whole cycle repeats itself:-(

I reinstalled all the cords of the hardware properly once again, reinstalled latest drivers in order to solve the problem but it was of no use, then later i uninstalled Direct X and reinstalled it but that was of no use too.
So then I decided to format the hard disk and install a fresh copy of windows, but that didn't work too and the problem still exists!! :-(

URGENT HELP NEEDED!!

I am also uploading the screen shot of the error here



Here the song played well for first 4 seconds and then the problem started.....

THANK YOU