Vista - no sound in Media center or media player

hi i have a sony diital living system VGX-XL2A that has been updated to
windows vista home premium. I have installed all the driver from sony that
are for vista. I am able to hear sound on start up and normal windows sounds,
plus i can get music when streaming frm MSN radio, BUT i can NOT get any
sound from media player or media center. both of them give me the error that
i have no audio hardware or it is not respnoding. To boot, my TV is also
frozen and does nothing. I am able to play DVD's and video files, but with no
sound of course. The people at sony could not help me, maybe you can thank
you!