Audio Menu > Audio Driver/Settings > Audio Driver Type

If you don't have an ASIO Sound Device you can install an ASIO DirectX Driver to use the onboard sound.

Edit: http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=236262&Searchpage=1&Main=33634&Words=ASIO&Search=true#Post236262