I don't know of any "quick fix" for getting sound working, but here is how I would proceed...
Do you have alsa installed (on debian, I would so "dpkg -l alsa*" to see what alsa packages I have installed. not sure if that is the best way to do it in ubuntu though)?
If you do have alsa, do some checks by following the advice at
You might be in luck, and everything might be working.
If it is not, i would
1) install alsa
2) find out what your soundcard is (use lspci to list pci devices)
3) find out if it is supported by linux
(even if the soundcard is not fully supported, you could still be able to use some generic drivers for it)
4) find the right drivers
5) install the right drivers
6) make sure other drivers are not in conflict with the right drivers.
the last two steps could get hairy if you are unlucky. but cross that bridge if and when you get to it.
you might find it helpful to try to boot from a live cd like knoppix and see if sound is working there automagically (kde often makes a lot of bell and whistle noises, so if you hear them, then you're in good shape). using "lsmod" on the command line could help you track down the sound drivers that are being successfully used.
and so....hardly a "quick fix" and more like a "trial and error, hope for the best, plan for the worst" approach.