I am not sure if you are really talking about JBoss Portal, what is the URL you are using to connect?
Ok your question is not related to JBoss Portal, you should really ask your question at: -
Before starting JBoss you should check if anything else is listenting on port 8080 (I suspect you have installed something else that is prompting for the password). You can check this with the command 'netstat -ao' which will also give you the process id of any process listening on the port.
Also when JBoss starts you should check to see if there are any errors in the console window during start up.
Finally if you should describe how you installed JBoss, if you used the installer you should say what options you selected.
Thank you - It was Oracle that was listening on that port