A lot of uninstall issues are covered in
this thread, although most of it relates to security issues. It's worth noting, just because you installed mIRC intentionally doesn't mean you are not infected with a trojan - a trojan may have hid mIRC at a later date from the Add/Remove programs list. There are numerous antivirus/firewall resources in
this thread.
Make sure you only get mIRC from this website, and try what Danman said.
Regards,
