I have identd on, port 113 forwarded and it worked for awhile, one day it stopped and yet everything is configured correct. I don't see why it won't work, either. Little help here please?
Are you sure XP Built-In Firewall has been disabled? I'm not only talking about packet-filter but the application-filtering for detecting applications acting as server, if that is still enabled you need to authorize mIRC application to it... Visit http://www.mirc.org/xpdccsp2/
And ZoneAlarm, make sure you give mIRC server rights... :P