MAME cannot be configured to NEVER display those. You can make a setting in the INI so you only see imperfect warnings once per game, but there is no way to always turn them off. They are hardcoded in the emulator to do that which is why to completely eliminate them you need a recompiled build that has that code removed or commented out (like the one provided by MadK9). You can also adjust the timer and number of key presses in your MAME Running Script to make the script work more accurately on your set up so you don't have to wait as long for the script to close those windows. For me 5 seconds was far better than the 10 we had defaulted, but that length of time can vary based on your computer and settings.