virtualbox.org

No audio in Win 7RC can be fixed by installing the Realtek audio drivers and then telling Win 7 to do an update.

Soudblaster cant work. You must use AC97 with an external Realtek Driver.

I had similar issues. My device manager in VB Win7 had a "Multimedia Audio Device" with the yellow exclamation It said the device driver was not installed. Duh! Windows update didn't work so I started looking for the ac97 driver that would work. After several attempts with other ac97 versions I found one that worked for me. I did the right click on the device above to manually install a driver and pointed it towards the downloaded and extracted folder(http://download.cnet.com/Realtek-AC-97- ... ?tag=mncol) with the vista64 driver version of the driver and wa la. I have the 64bit vista host and the win7 64bit guest. The downloaded file has the 64 and 32 bit version inside. Worked for me. I think it is just a matter of finding the friendly(or not so friendly) compatible driver---if this doesn't work for you. Hope this helps someone. PJ