Here's what I did to solve that problem. I just stumbled on it because I forgot what I did and had to do this again for another computer.

In Control Panel>Hardware and Sound, click on "Change system sounds"

In the menu under the "Windows" header, find Select. I created a short wav file with less than a second of no sound, called it "No Sound.wav" and put it into the C:\Windows\Media folder. In the drop down box below the menu, I have No Sound selected and hit apply. This could be another option if you aren't able to change/see the "Beep" selection in Computer Management.