I posted this originally as a reply to another post but figured it would get a bit more exposure here:
A mIRC installer that automatically finds the mIRC directory (or maybe lists all directories mIRC is installed in if theres more than one installation? That you can checkmark which to install to and have multiple?), puts whatever files there, and then performs certain mIRC commands to install it (IE automatic script loading)
..kinda like Winamp's installer.
