If you've removed all of the registry entries for mIRC, and manually deleted the mIRC directory (and any other references to mIRC on your system, excluding the mIRC installation program), make sure you reboot your system, then connect to the internet, then install mIRC, ensuring that the first two checkboxes in the installation dialog are unchecked. The third one doesn't really matter, it's just for the icons. That should give you a completely fresh installation of mIRC.
If that doesn't work, I'll need to know what version of Windows you're running, including if you have all of the updates for that version or not...If you don't have all the updates, I'd recommend you get them.
