I've never tried to completely delete a desktop theme, but right-click on Desktop, click Properties | Themes; open the drop-down menu and highlight the annoyance to delete it. If that doesn't work, try Control Panel | Sounds and Audio Devices | Sounds, see if you can find the offending file or theme. If that doesn't work, and you have a few hours--do what I did a while back. I was so P.O.'d at one sound I couldn't find that I used Search to find *.wav....found it that way.