Hi Recently i have installed the last version off mIRC, but i have noted that the mirc is running under a "temporary" folder, that mirc creates in ...\Application Data\mIRC\.
If mIRC finds mirc.ini in the same directory as mirc.exe it will use that directory. If you're running C:\mirc\mirc.exe and there is a mirc.ini in the same folder then that dir will be used.