Q: Trouble accessing wireless network

I am trying to access a wireless network via an Original Airport Card in a PPC G4Powerbook.  I have selected the Networl name and inputted the password numerous times and selected other Network without success.  I had accessed the network once before, but now my computer does not automatically log onto the network.  Is there somewhere whre I can go in my computer to zero out ALL NETWORKS I  have accessed and start from scratch or any othersuggestions that might solve my dilemma?