Cannot change new mail sound...other system sound problem

Recently, my machine started using the default beep sound for new mail
notification.

I tried changning the wav file in the sound settings pannel, and it DOES
successfully play when you push the play button, but the default beep
persists. I even checked the registry, and the registry shows the wav file
that I selected.

I have installed the most recent drivers (after the problem occured)...

Other system sounds use the default beep as well (not all) even though
another sound is assigned.

Help!