So I have a Ubuntu 10.04 host that has a Windows 7 Enterprise guest that has no sound because the Multimedia Audio Controller driver isn't auto-detected by Windows. The solution is to update the driver with the Realtek driver as told by the following blog.
Woo hoo, sound! Now to plug something into the speaker/headphone jack. :-)
http://heratech.net/blog/sham/virtualbox-windows-7-no-sound-multimedia-audio-controller-driver-missing
--Chris
LABrat.com
