I only have the same information for you that is available on the website, namely - "IRClean is a 100% free, standalone, compact (32kb total download), and easy-to-use yet very powerful anti-worm system designed to specifically combat worms that target or use IRC chat networks to propagate. It has been released into the public domain for free to help stem the growing tide of IRC-propagating worms.
MIRClean integrates IRClean within MIRC giving you automatic scanning of downloaded files and various other automatic abilities. . Created by Nicholas Hillebran"
Removing every piece of malware is not something that one program really achieves on its own, it is a case of multi-pronged attack using several reputable programs designed for malware removal.
I suspect, (but could be wrong) maybe you have been surfing the Internet as an Administrative user rather as a Limited user. This (if it applies), is not a very safe practice.