lost startup and shutdown sounds XP

I have lost the startup and shut down and other operatonal sounds on WIN XP. If the sound icon is opened the slide bar moves with mono tone inside the computer instead of through the speakers. There is normal program and playback sound through the speakers otherwise. It appears to be an operating system glitch. I do have functional sounds by testing in the control panel and all sound devices are working. Annoying problem which others have also experienced. I am using a MSI mother board with integred intel sound. Any suggestions?