No system sounds or internet sounds. but media still works

Hi there
I am having a problem with the playback of system sounds and also sounds
from the internet such as embeded music and video.

The problem only started a few day ago and there was now definite cause.

Music and video play normally through all other programs such as media center.

I have updated all audio drivers and also uninstalled cleaned and
reinstalled them.
The correct audio device is set as default and all volumes are set to an
acceptable level.

The OS is Vista Home Premium.

Thank you