Please write what webcam you using with your yahoo messenger? and what is the camera type Desktop or Laptop built in? I think your webcam driver is not digitally signed...And in that purpose you could receive an error pop up or error box during installation containing Stop Installation or Continue Anyway...Try to use any branded webcam like Microsoft, A4 tech, Sony, Logitech etc... I think you can get my point... For further asistance please be with Fixya....Thanks and Good Luck