Problems with audio in windows xp sp3?

A friend's pc has no audio as far as windows system sounds or anything on the internet. I have already gone to control panel and made sure that the audio device was enabled and functioning properly and checked to make sure that none of the mute buttons were checked. The volume bars are set to max and the realtek control panel also shows the sound functioning and enabled. If I start a movie, game, or cd the sound works fine. The realtek control panel has a sound check button where a tone is played through each speaker and this also works. So, the sound works completely fine for everything but windows system sounds(set to default sounds) and internet explorer. Does anyone know where the problem in windows is and how to fix it? Thank you.