Thanks for the advice and the link, but unfortunately to get this “free” download you have to “participate” in something first.
The XP firewall has a simple and small graphic interface but a rather complex set of command-line (CL) parameters available ‘under’ it. There is a simple CL command to reset XP’s firewall CL settings to default: Start, Run, CMD, then: NETSH FIREWALL RESET.
My advice is to follow others’ advice and install a 3rd party (free) firewall like Zone Alarm. You could also install Avast! free anti-virus which has a free firewall with nice features. Before going to MS Security Essentials Avast! was my AV program.