What? You just put Norton Antivirus in, right? If it so, then you don't need to configure anything. Antivirus programs are not firewalls.
If you put Norton Internet security, then you've also put in the firewall. You'll need to configure that. Same goes if you just put Norton firewall in.

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iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-