Run the application gconf-editor, or alternatively type it in terminal. Go to apps/nautilus/desktop and uncheck "volumes_visible." Voila. However, this means that USB drives and other mounted volumes won't show up, either. My ideal solution is to just have my Windows partition hidden and have USB drives show up when they're needed. Edit: I actually just turned this off. I edited the fstab to mount my Windows partition to a hidden folder, so it won't show up. I can still access it, though, as well as have icons for USB drives.