You will need to download the drivers from
Intel, download the latest version of
alsa, or get Fedora Core 5 when it gets released next month (FC5 test 2 audio works - I know). Fedora Core 4 doesn't fully support Intel chipsets natively past the 865/875 chipsets.
The simplest would be getting the latest stable drivers from alsa, 1.0.10 I believe.