Wireless networks messages

Whenever I switch on my PowerBook G4 (still on 10.3.9) two messages appear about wireless networks - the first being 'None of your trusted wireless networks can be found. Would you like to join the open wireless network named "name"?'. I click No to that and then another one comes up a few seconds later - 'None of your trusted wireless networks can be found. Would you like to join the open network named "differentname"?'. As soon as I clear these I can connect to my home wireless, however it's get annoying and I don't know how to stop these appears, there appears to be nothing in preferences?