As a joke I went to download the Ringjacker, I was warned that this wasn't supported by Skype, but decided to anyway. It is supposed to change the ringtone of the receiving mobile phone, as a joke with a selection of imput ring-tones. But don't download it, it doesn't work and you'll find a line error when you boot up your computer. I've tried to get it out with search and destroy, but its there again when I boot up.