Beep in Word 2000

I'm running Word 2000 on Vista (I can't get used to 2007's interface) and
every time I open/save/click a file in the explorer window, it makes a short
error beep. It does the same thing in Excel 2000, but when I use Excel or
Powerpoint 2007, the beep is not there.

My sound scheme is on no sounds, and I did disable the "provide feedback
with sound" option in Word's options.

Can anyone tell me how to disable this beep, or at least where I can find
the sound file to delete it?