Hi zz30fg,
Beep codes can be used as diagnostic indicator.System can emit a series of beeps during start-up if the display cannot show errors or problems.Single beep code indicates the computer encountered a possible system board failure(BIOS corruption).
Do your hear that beep sound every time to start the system (even when the system starts normally) or do your hear that beep sound only when there is no display (or no lights on the keyboard or mouse)?
Is your system covered under warranty?