Usually if you get sound device is used by another application there IS another application that failed to close the sound device properly. The latest Napster version is notorious for this, beta 6 seemed to be good about this but beta 7 seems to latch on to the audio device now and again (Even when you've named another application to play sounds.)(posted 8822 days ago)other windows programs might be able to play sounds when the audio device is locked because windows sometimes "mixes" new application sounds into currently existing applications, but mame doesn't have the power to do this.