I can't find a way to shut mine up ther but I set the ringer to an MP3 you just have to find the one you want and drop it into the windows directory.
I got mine from
www.tuneusin.com not the best website but they have some short MP3 SFX files for free.
Click on Ringtones >scroll down on the next page and select SFX they don't have a lot but you may find one you like I did. I used the Star Trek original intro from themes. It is like 8 sec and loud.