User Name – Drop Down – How 2 Delete

I can’t seem to find a way to do such a simple thing – You know when you log in to MSN Messenger? You click on sign in then if you have signed in there before it keeps your user name in a drop down. Well, I want to delete someone’s name who used my pc to access their MSN. I’ve tried a right hand click, and delete etc, but can’t seem to get rid of it.

I’ve even tried to un-install the whole MSN and re-install it, but that didn’t work.

Please help.