Wow.. So old school :p I found the file for 5.11 but that was the earliest i could get, no better place to share than here. I couldn't believe what the old school mIRC looked like, infact.. not a lot different..
Older versions (not just for mIRC, but also many other programs) can be found on http://www.oldversion.com
Here you go Jonesy44
http://www.mircscripts.com/old/
from Mirc6.21 down to Mirc2.1a