windows volume adjusts automatically... why?

[-N-]

For some reason, my volume meter in the control panel adjusts by itself automatically. the "wave" setting is always lower to some level. I change it back to max and forget about it. Then some time later, maybe the next day or something when I play winamp i notice it's softer and alas... the volume adjusted again by itself.

I suspect it's some program changing it but I'm not running anything that requires sound.

help? :bang head