Ah....well it may matter. Don't know. Several other gamers I know who have Vista have had to re-install their components
and drivers several times.
I do not know VIsta but I'll have you check one other thing.
Go to "Control Panel" if Vista has that and select "Sounds and Audio Devices".
I want to see if you can get to a Window that looks like this -
Select the Audio tab at the top.
Within the Audio tabbed window you will see "Sound Playback" and than a "Default Device" line.
If you get that far - can you click on the drop-down arrow to the right?
Do you have two or more choices for devices? SO, for example this image shows "Realtek AC97 Audio".
If you click on the drop-down arrow is there another or more choices? Can you get a screen print of that
If you can't get to the Audio device list than the only other thing that I can think of is to have you
un-install and re-install your Audio card and drivers.
By the way, you did say that it is an Audio card that you connect to, right? It is not a USB headset?