Sound Only Partially Working (Vista)

Recently my PC succumbed to a virus, which disabled my USB and only allowed for partial sound output. The computer was reformatted and troubleshot to have the USB working again, however the sound is still only coming out at a very muted volume. A quick glance into the device manager is showing me that, yes, a High Definition Audio Device is installed, and to be honest I'm not sure if I should trust if that is in fact the correct name for the driver... Any suggestions as to how to rectify this problem would be greatly appreciated.