Question: Can I create a custom version of the mIRC distribution files, or distribute mIRC as part of my script?
Answer: Sorry, this is not permitted by the distribution license. If you are creating a script, you must distribute your script as a separate file, and ask users to visit the mIRC website to download mIRC if they don't already have it installed.
What's wrong with Self Extractor? Sure it's not exactly a feature-bound programme, and doesn't add the desktop icon of the .exe file inside, but if all you want to do it pack up files, shift them somewhere and then unpack them again on a computer with no unzip support then Self Extractor is perfect for the task.