How about this. Disable all your sounds in Windows. If this is the standard "Ding" Windows uses (I also have W2K Pro), then after something is accomplished, it notifies you with a ding. Try it and see if that stops the sound. Remember, I'm not talking about all sound across everything, just the native Windows sounds you can change in Control Panel. If that's it, then look for a program in the background that is running and may contribute to this.