Finally, I reformatted the pc. However, the sound issue still remains in a couple of games. Hmmm... I'm going to try and figure out what's causing the issue 'cos I'd already tried the onboard sound, swapped speakers and even used headphones.
I suspect something's interfering with the sound on the system but what? Oh well... I'd already re-arranged the wires. And I wonder if it's 'cos of the PCM Converter.