[PC Game Tech Help] Can't get sound on ArmA II to work

I've spent probably a combined 6 or 7 hours over 2 days trying to get the sound on my new copy of ArmA II: Combined Operations to work. My sound works for every other application, game, etc, just not for ArmA 2.

I'm running Vista 64, and I've downloaded the latest patch for the game.
I've tried:
*installing various DirectX redistributables, including the March 2009 one which some people said fixed the problem, also tried the one off the disc, and the latest June 2010 one.
*installing latest Realtek sound drivers.
*installing generic windows sound drivers.
*installing openal drivers.
*messing with the config file for the game, which apparently is supposed to have a couple options called soundEnableEAX and soundEnableHW. Neither was in config files, so added both lines and tried all combinations of setting each to 1 or 0.

...none of this worked, of course, or I wouldn't be here. Does anyone have any ideas?

 

I did see someone suggest that, and when I went to do that there was no icon for it at all.

...does that tell you anything? I've never run into a sound problem quite like this one myself...

 

Thanks a bunch for the replies.

Yeah, I only have stereo and the output is set as such, so that can't be it. I'm truly baffled.

How well do those in-place upgrades work? I just have so much crap installed I really don't want to bother doing an upgrade from scratch...