It would really help if you could try to narrow down the cause of this issue. I'd suggest closing down all background applications, including anti-virus/firewall software. If mIRC still doesn't run, open Task Manager and close down other non-essential background applications and then try running mIRC again. If mIRC still doesn't run, try restarting Windows in safe mode and then run mIRC. If mIRC still doesn't run, try copying mirc.exe into an empty folder with an empty mirc.ini file and then running it.
