In Chrome/Opera/Safari versions, you can go to X-Notifier's Options ...to make sure 'Play a sound' is checkmarked, and to select a custom sound file. In Firefox/Sea Monkey/Thunderbird, you go to X-Notifier's Options, then click the 'General' tab at top... then you can make sure 'Play a sound' is checkmarked, and select a custom sound file.
Options
In Chrome/Opera/Safari versions, you can go to X-Notifier's Options ...to make sure 'Play a sound' is checkmarked, and to select a custom sound file.
In Firefox/Sea Monkey/Thunderbird, you go to X-Notifier's Options, then click the 'General' tab at top... then you can make sure 'Play a sound' is checkmarked, and select a custom sound file.