Many old machines, especially old laptops or notebooks, have no soundcard. On-board soundcards in notebooks came in the late Pentium-I-era, before that the laptops were silent, except for some beeps from the pc speaker.
Here are instructions how to turn your 486 laptop into a multimedia machine
I have precompiled a Kernel for DeLi Linux patched with the pcsp driver from here.
First get the following packages:
Warning: This kernel is only for IDE-Systems, don't use this, if you have a SCSI system.
installpkg linux-126.96.36.199pcsnd-i386-1.tgz installpkg aumix-2.8-i386-4.tgz installpkg mpg123-0.60-i386-1.tgz installpkg sox-12.17.9-i386-1.tgz lilo # The new kernel will be installed
Then reboot. After that do
Thats it, your machine is now ready for sound. First set the volume to maximum with
aumix. Then get some MP3s and play them with
mpg123. If you have the usual 128k MP3s it will help to use
mpg123 -m -4 MP3file to spare CPU ressources.
The pcsnd driver eats a lot of CPU, but mpg123 on the console works fine. The result is very good, compared with the sound driver for PC speaker from old Windows 3.1 back in the old days. Don't expect miracles, this won't be exactly a replacement for your hi-fi system, but the quality is comparable with what small 5$ non-active speakers will produce.
You can try to use xmms, but on my 486 laptop xmms needs too much CPU ressources and the sound is choppy.
A few years ago I used something like http://de.wikipedia.org/wiki/Network_Audio_System for this situation. Delete this if it doesnt fit as a workaround in this situation.