To check things out, issue:
/sbin/modprobe sb io=0x220 irq=5 dma=1 dma16=0 mpu_io=0x330
as root. If there's a high pitch squeal, it's working and there is feedback from the built-in microphone. (Turn the volume down with the physical controls, for now.)
Edit /etc/rc.d/rc.modules and uncomment the "/sbin/modprobe sb ..." If the line is not exactly /sbin/modprobe sb io=0x220 irq=5 dma=1 dma16=0 mpu_io=0x330 edit it so that it is.
After that line, add a new line:
aumix -L
This will load the mixer settings (that need to be created).
To get rid of the squeal takes a bit more work. Log in as a user and open a terminal. Run aumix and adjust the settings (turn the microphone down to 0). Save the settings. The setting should be in the .aumixrc file in the user directory.
Become root. Copy the .aumixrc file to aumixrc (no leading dot) and then move the new file to the /etc directory.
The sound will now be activated during boot and the squeal will be there for a short time (a second or two) and then the mixer levels will be loaded and things will be quiet.
As the drive seems not to have dma and the dma stuff on boot hangs and makes the boot longer, add ide=nodma to the append="..." line in the lilo.conf file.
To enable booting to the diagnostic partition, add the lines (assuming that the diagnostic partition is /dev/hda4):
other = /dev/hda4
label = "Diagnostic"
at the end of the lilo.conf file.
Running lilo may give if an error if the name is too long. (I got frustrated after a few attempts and used the label DamnBIOS... that's short enough.)