Had you clicked on the link Nimue kindly posted, you would have seen:
Most installation processes that specifically stop with urls.ini extract problems are caused by DDE conflicts with applications running in the background during mIRC's installation. As clearly advised when installing mIRC; close all (*all*) other applications before you start mIRC's installation.
As the original poster described exactly this, it is highly unlikely their prob would have anything to do with corrupt files or trojans.
