|Original post content modified for Vista.|
NOTE - The mboard I looked at Vista in has 5.1 or better onboard sound, but I have only a pair of speakers connected to that, so I'm guessing what you should see.
RIGHT click on the speaker icon in your taskbar lower right.
Select Playback Device -
Make sure the the Audigy is selected as default, and highlight it, click on Properties
Select the Levels tab.
You should see volume controls for Front, Rear, Center, Side, and Subwoofer or similar.
If you don't see any, or some, of those, click on the Enhancements tab, and click on the small square blank box beside anything listed you want a volume control to appear for.
Adjust the volumes to whatever you want that sounds best to you.
If that doesn't help, (if Vista didn't auto install the sound drivers and associated software) use the Audigy's own sound utility, which is probably in Control Panel, and/or in your Programs list somewhere - e.g. you may have selected some sound configuration that makes the rear speakers echo-y.
If that doesn't help, as with many SoundBlaster / Creative cards and built into the mboard SoundBlaster / Creative sound chipsets, there are several possible Audigy sound chipsets - are you sure you installed drivers and associated programs for the correct one?? The drivers on a CD that came with the physical card, or that came on the mboard CD if it's built in, or that are available in the software downloads for your model on the brand name builder's web site, are correct, but drivers you have downloaded from the web may not be.
It is often a BAD idea to load drivers for a device while booting before the software for it has been installed, when Windows detects a device while booting, you have it look for drivers, it doesn't find any or finds only a generic device, then you point it to the location of where you have drivers - in many cases at least some of the software won't work properly or is missing if you do that, and/or the device won't work properly in at least some situations. CANCEL that, let the desktop load, THEN install the software for the device using it's proper installation software package, following the installation directions (sometimes those are within the contents of the software you downloaded, or consult the manual for the device).