First, open mirc and press alt+R. When the window appears, paste the code i made above into that window. Click okay at the bottom.
Next, locate the file you want to play when you get a msg on your computer. Right click on it, and select "copy". Next, open mirc and type
/run sounds\ This will open your mirc sounds directory. Paste the file into this folder by right cliking in the window, and select "paste". Now, right click that file and rename it (if it isn't already) to a file with no spaces (Just makes life easier).
Next, close the folder window, and re-open mirc. Press alt+r once more, and find where it says
dir\sound.wav Rename this to
sounds\[color:green]file_you_just_renamed.wav[/color] Click okay, and Viola!