I found a small glitch while installing Ubuntu 7.04 - the Feisty Fawn on my acer aspire 5100. The audio was coming out of one channel only and there was no record capability. The solution was to recompile alsa. Its not as bad as it sounds, from a console type

sudo apt-get install build-essential to install the necessary software to compile it all.

Download the following file alsa-driver-1.0.14.tar.bz2 by clicking on it and from a console go into the folder you saved it to and type

tar -xvf alsa-driver-1.0.14.tar.bz2 to extract the compressed file
cd alsa-driver-1.0.14 to go into the folder you unzipped
./configure --with-cards=all --with-card-options=all to configure the installation
sudo make to compile it all
sudo make install to install the compilled files

This has worked for me and it allows you to keep your graphical system intact. There is another way to do it but it involves removing the graphical system uninstalling the audio system, reinstalling it and reinstalling the graphical system.

To do the alternative way from a terminal type in

sudo apt-get --purge remove linux-sound-base alsa-base alsa-utils to remove the packages and configuration files

This will also uninstall gnome-desktop which is the package used to give you a graphical display, dont panic we can install them after.

Then type in
sudo apt-get install linux-sound-base alsa-base alsa-utils alsamixer to reinstall the sound system plus a neat text based mixer

The sound in all functionality should now be ok, to get the graphical display back we just reinstall it by typing
sudo apt-get install gdm ubuntu-desktop

Reboot the computer and your regular login and desktop should be up and running with perfect audio. Use the alsamixer program to modify any audio levels. It is text based but I find it far superior to anything graphical