Comment 42 for bug 369000

p.s. by "enable the on-board sound", I mean enabling it in the BIOS settings. This is by pressing F2 or F12 or F10 during boot (can' remember which) to get to the BIOS menu, and then go and enable it.

You might want to make sure it is enabled. If you have sound on any other OS (i.e. Windows), then the BIOS setting is not the issue. If on-board sound is disabled in the BIOS, then sound is disabled for every operating system, until you re-enable it.