Exactly as I said above, in my last (complete) sentence. It's the only
thing I can think of - but *please* don't ask me how that might have
happened
Aside to Bogey man - find a wav file that works, copy it into the same
folder as the system sounds, and assign it to some event. Now see if you
get that sound properly. Choose a short sound - Beethoven's Ninth is too
long
If that works, the other files there are corrupt; if not, something is
messed up in the logic used by Windows to find those sound files. Of
course, you could test the other system sounds directly in your favorite
player, as I already said.