And finally, I loaded up DDESpy and did not see Mirc using DDE commands to start FireFox.

Does anyone know which underlying mechanism Mirc is using for launching the browser and passing it the URL to open?

DDE is a way for applications to send data back and forth (a few winamp NowPlaying scripts use DDE)

afaik, mirc proly uses a shell command and just sends the page address to it. Its like all .txt files will open with notepad by default. Windows will just open all http data by whatever is ment to handle it (firefox, IE,netscape, whichever)