Try going to add/remove programs (start -> control panel -> Add or Remove programs), and look for "mIRC".
You should also get someone to help you removing the autorun from the registry.
You can also search for "mIRC.exe" on your harddrive, and tell us what file names are in the folder, incase it installed itself in a windows directory.
Also, this program should not start on its own. It also doesn't start up again when you close it. It looks like you downloaded it from a malicious site/mirror.
