Is there a chance that u have installed a prog which at some point provided an option to install yahoo mail/messaging, or not? I had this option recently on installing a game and chose not to install. Might be worth checking in ur prog files for a 'yahoo' folder. Failing that go to ctrl panel/settings/add/remove progs and look in there. If u still can't see it, get ccleaner and look in Toools. This will tell u what u have installed.