I don't run XP so I can't tell you exactly where the disable box is. But Norton & XP's firewalls should NEVER be run together. They are reknown to clash with each other. Turning it off/disabling it .... I'd have thought the same thing but I'm not a XP user so not sure. Did you check the other method mentioned about disabling XP's firewall.

When updating LW sometimes Norton gets confused, so ... Reconfiguring Norton Firewall