Netscape Navigator stores usernames and passwords for web sites which you have logged in to.
Password storage is configured in Netscape Navigator under <Edit>, <Preferences>, <Privacy and Security>, <Passwords>.
By default, Netscape Navigator stores all passwords unencrypted.
Viewing Netscape Navigator stored passwords
The usernames and passwords are stored are part of the Netscape Navigator user profile.
The location of the Netscape Navigator user profile varies between versions and installations.
My Netscape Navigator user profile is stored in C:Documents and SettingsWillApplication DataMozillaregistry.dat.
Netscapass will help you view stored Netscape Navigator passwords:
Recovering Netscape Navigator encrypted passwords
I am not aware of any currently existing software to decrypt Netscape Navigator encrypted passwords.
Known weaknesses in the password encryption system of Netscape Mail lead me to believe that an application of this nature could be created, and simply has yet to be written.