In windows explorer, navigate to "C:/My Documents/Username/Start menu/Programs"
Any programs listed in "All Users/Start Menu/Programs" will be visible to erm... all users, whereas programs visible to specific users will only be listed in their particular Programs folder. Thus, if your Dad's stuff is in "All Users/Start Menu/Programs" then you'll see it even though it's not in your list.
Within your "Jayko/Start Menu/Programs" folder, you can add and delete to your heart's content.
Make sure your Dad's stuff is only in his (not the All Users) folder and you won't see it. Or, right-click on the errant menu item and delete it. If a window opens saying this action will affect all users of the computer, never mind
