Karen is having trouble with her MacBook Air running OS X Mavericks. She didn't like it and decided to install Windows on it with Boot Camp. Now her sound doesn't work. Leo says this be happening because she got rid of OS X to put Windows on it, and Boot Camp drivers aren't supported on Vista. She'll have to install Windows 7, and that would require re-installing OS X again.
Leo also said that according to the chatroom, if she installs Vista Service Pack 1, it should work properly.