I had a simular problem once. Though I cant recall the exact particulars.
Gist of it was, there was another application running in the background possibly windows media player, winamp, or musicmatch jukebox etc. Whose master volume control was set at zero. It would reset the windows volume control every single time you tried to adjust it. In other words the volume control of the other application had taken over control of the situation.
It's perhaps a long shot, but you might want to check what you have running in the background and check it's volume settings.
George.
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Dutch
Dutch
I came, looked around,
and decided to stay awhile.