why the front speakers/channels have no output

I am having problems taking full advantage of my system's audio
capabilities. I have a system with the following configurations,
hardware, and software settings:

System:
Pentium 4 (3GHz, 1GB RAM)
Windows XP Home Edition, Version 2002, Service Pack 2

Sound Card:
SoundBlaster Audigy 2 ZS [A400]
Driver release: release 2.9.16 (re-installed to ensure that it is not
corrupt)

Speakers:
Logitech Z-5300 Speakers
Source selector switch: 5.1
Matrix: on

Audio Software:
Creative Audio Console:
Speakers: 5.1 Speakers (synchronized with MS Windows Control Panel)

Control Panel - Sounds and Audio Devices
Speaker Settings: Speaker Setup: 5.1 surround sound speakers

When listening to music - .mp3 or .wav (off a CD) - or a DVD, or
playing material via iTunes (music and video), the front speakers/
channels (left and right) not producing any sound. Center speaker/
channel is playing about 80 percent of non-sub-woofer audio (operating
normally), with the rear speakers/channels (both left and right)
producing the other 20 percent.

I'm trying to determine why the front speakers/channels have no
output.

All the wires/plugs are connected properly. All the hardware
configurations and software settings appear to be correct. I've
reinstalled the sound card driver and audio software (WinAmp). I just
cannot figure out why there is no front speaker/channel sound.

Can anyone help me?