[Emcha_audio]

Do you by any chance start Windows without having the Mbox powered on? If so, Windows will revert to an other set of "speakers". If you have set the Mbox as the default audio device in Windows (start -> Control Panel -> Sound -> Playback tab) you will see a green check mark beside the mbox. if you don't see it beside it, then it's not the default audio device and this is probably why you are having problems.