I realize this is from a while back, but..
You can try upgrading the ALSA drivers to the latest versions to see if they have better support for your computer's sound.
To upgrade the ALSA drivers, you can add the driver repository for my distro to your sources. Although this repository is meant my distro, all the packages on it will work perfectly on Ubuntu 9.10.
You can check and see what packages my repository includes by going to https://launchpad.net/~infinityos/+a...esting-drivers
To upgrade the drivers and add my repo to your sources, enter the following commands into your terminal:
$ sudo add-apt-repository ppa:infinityos/testing-drivers
$ sudo aptitude update
$ sudo aptitude dist-upgrade
You will need to restart your computer after those commands are completed.
If that fails, trying removing PulseAudio. PulseAudio seems to break everything related to sound on Ubuntu. Remove it by following the instructions here:
Note: I realize I copied this stuff from another answer of mine, but the instructions are basically the same.