My Realtek audio system works well for the internet, for music disks in the
CD player, and for wav files on my hard drive. It does not play anything
coming in to the line-in jack.

The turntable is plugged in to a pre-amp and that into the line-in socket of
my mobo. When I play a vinyl record, I hear faint sounds from the speakers
that increase as I increase the gain of the pre-amp. Total Recorder
(software) transfers this audio into a wav file which plays back just fine.

In a previous incarnation of XP-pro on this computer, I could hear the
records as they played on the same pre-amp. I have no idea what the
differences were between this install and the two subsequent.