Ubuntu 9.10 Audio is poor with sound cuttingin/ out

While playing mp3 music file the sound is of poor quality and then cuts in and out.
While attempting to trouble shoot I did stumble on an audio application which showed the music was switching from mono to stereo mode when the music was cutting out. Not sure if that is a symptom or a cause?

I am not sure if this is related. But I can not get Win7 audio to work at all. It is installed as a virtual machine in Virtualbox 3.1.
In this situation win 7 does not detect the HD audio built into the mother brd and therefore won't install audio drivers.
mother board is an ASUS M4N78 PRO with a 64 bit quad core AMD processor.

I am thinking that maybe I should purchase a separate PCI audio card?

Any idea's or suggestions will be greatly appreciated.