Quote from Big AAPL:
You're not necessarily 'replacing' the default sound files, you are simply calling up a custom .wav file when you program a strat or market analyzer. For example:
You program a simple strategy to play a sound file whenever the MACD Fast line crosses zero. You use a custom sound file that is unique to that particular strat so as not to get confused by using all the default sound files such as " cash register ringing", or "Alert 1 (buzzer)" , and so forth. Furthermore, you can use "cross above" and "cross below" in a number of computer generated voices easily found on the web. I actually use some old Quake .wav files like "Rampage!", and "Humiliation" for certain situations.
Program Files > NT 6.5 > Sounds > Place .wav file here.
I'm not sure how large a file you can use, and I keep mine short and sweet.