You don't need to worry about the registry. All you will really need are the INI files and whatever script(s) you are using. If you want to copy the entire mIRC folder, that will be fine. However, if you're using 6.3, you will want to also copy the mIRC folder in your appdata folder under your documents and settings folder as this is where the INI files may be located for you.
#Invision on irc.irchighway.net