The sad thing about that kick reason is that Ä is not the only file that can produce the auto-advertising that you could be sending. There is also server.ini (not to be confused with servers.ini which is a proper mIRC file), aliases.ini (in some cases, not all - Pays to know your script here!), script.ini, (again, know your script!), - (no file extension, just the dash as a file name), and a few others.
It pays to know what files you normally have in your mIRC directory. It also pays not to visit websites that get advertised on IRC as this is how you would have picked up the file to begin with. Some websites can shift a file called rol.vbs to your machine which rewrites itself to your mIRC directory where-ever it is, it doesn't need to be on C:\mIRC. There's a few different versions of rol.vbs. Some just make your script an adbot (as it appears yours has) and other versions also add a warbot to your script which can be used to DDoS an IRC server. You'll never know you are doing either of these things until you get told because all the inputs are prefixed with a full stop which stops them being echoed to your screen.
Where I chat, we don't often get this problem, hence the lack of a dedicated room aimed at virus removal techniques. On the odd occasion that someone does get infected we place the URL or part of it in the IRCd's swearfilter so it looks like this...http://www.*********.com/******/**********.htm
(Swearfilter puts stars in place of the words)
...and then we write a formal complaint to the webhost which results in the site's removal inside 24 hrs.
How can I prevent this happening to me? The most common way is visiting advertised websites. Most official IRC/channel websites can universally be trusted but anything news, porn or sex related, steer clear of it. Avoid it like the plague.
One other thing you should do too is have anti-virus software. Most brands will pick up files like rol.vbs as you download them and this is the best way to remove those files before they do any damage.