This is what I did:
I could not uninstall the Audio card driver since it did not show up under the Audio Devices in the Multimedia Properties applet and the Audio Devices directory.
I tried installing the audio card driver 2ce from the network and rebooted, and still no luck.
I added the driver to the Mixer Devices and then rebooted. No sound volume yet but it was in the Mixer Devices.
I then uninstalled it from the Mixer Devices and rebooted.
I also changed the Workstation Services from the Services applet to Automatic instead of Manual.
I then installed the driver from the network and rebooted it.
And... Voila! now it works.
I would like to replicate the problem but I'm not sure where the problem originated but it began with the installation of a new network card and a subsequent IRQ conflict.
But why is there no conflict now since the network card is still there.
I wonder if I reinstalled the network card if the problem would reappear?
Anyway, thanks to all who tried to resolve the problem for me.