I have recently removed my PCI bus sound card from my PC and started using the onboard sound, to make use of the six channel facilities built on to the motherboard. I use to have audio cables going from my DVD ROM and CDRW drives into the, now removed, sound card. This was so that audio type media could be played from these drives and heard through the speakers. Now on my motherboard there is only one connecter for the main cdrom drive which is the DVD, so I plugged in the audio cable from the DVD drive to the motherboard. I powered up and I put in a music CD and it could be heard perfectly. So I thought if I tried it in the CDRW it would not be heard, but it was! SO I removed the audio wire completely from the DVD drive and out of the system, tried a music CD and it worked.
Why does it work?, is it because I am making use of the onboard sound, and these drives are already connected to the mb, via the IDE cables?
I have never actually tried any music CDs while the other sound card was in, without connecting any of the audio cables to it.