“Webserver is already running on Port 80

Problem: Initial sign on to XP Pro OS after password I now am getting the following error message: “webserver already running on port 80. Shut down application and restart to avoid conflict” (last part isn’t quite right but frst part is verbatim ) I can’t locate what application is doing this and how to stop it from loading up. Can you guide my feelble brain to the answer and what to do after I find it? Thanks