One of the applications that I wrote and maintain here for use at my job is a C# Windows application. A couple of revisions ago I set it up so that the user could press the Enter key to submit the login instead of having to click the actual login button. For the longest time now this has produced a beep sound. ANNOYING!
I finally took the time to address this. On the text boxes I was catching the KeyUp event and checking for the Enter key. Come to find out that to properly make sure that the WHOLE event gets handled I needed to use the KeyPress event, and set the Handled property to true so that it would not flow back down to the key event handler on the form. Now, no more beep!