Those addresses are ones you recently sent to, and they are stored in
a key in the registry.
Unless you are familiar with editing the registry, I would
advise you to ignore the problem for now. Eventually
the unwanted addresses will drop off the remembered list.
If you are proficient with registry editing, the pertinent key is:
HKEY_CURRENT_USER\Software\Microsoft\Windows Mail\Recently Used Addresses
Gary VanderMolen