As mentioned in my last posting on OpenSuse 10.2 in Virtual PC 2007, I could not get sound to work. After just installing Mandriva 2007, I encountered the exact same problem. After a little research, I found the answer here: http://www.linuxquestions.org/questions/showthread.php?t=149181
As I have already deleted my OpenSuse VPC image, I wasn't able to test and see if it worked, but I can confirm that sound works in Mandriva 2007 (within Virtual PC 2007) with the above steps. I hope this helps someone out!