Hi all,
I want to ask the purpose of the little audio cable behind the Cd-Rom drive. I don't have it connected and I can listen to audio CDs perfectly !

Thanks

It's a legacy connection.
Originally you had to connect it to be able to hear standard audio CDs - all other sound went through the data cable.
If your optical drive is less than 8 years or so old, the optical drive is wired such that the sound that port provides is sent through the data cable as well.
Sometimes you have to set Windows to use the digital input if it isn't detected automatically.
You don't need to connect it unless you want to be able to modify the sound some way you can't when it is sent through the data cable - e.g. you can connect a cable from there to pins on a sound card or onboard sound input and process the sound through the sound chipset's mixer circuits directly.

Yeah, the 4-wire cable is just a speaker connection. When it's used, the music pretty much bypasses all the computer's software and hardware and is fed directly to the speakers. With the cable connected you can even play music in dos with no player software running.

I know the 98 default cd player needed the cable installed in order to work. But WMP, winamp and all the other software players process the signal through the IDE connection and not the audio cable. So when using those, the audio cable is irrelevent.

"I know the 98 default cd player needed the cable installed in order to work."

I still use 98SE most of the time. If the CD drive is new enough, you don't need to connect the cable.

Even when you go through PROGRAMS--ACCESSORIES--ENTERTAINMENT--CD PLAYER?