WindowsXp ding.wav does not sound when releasing Play Control Slider in Volume Control

Running Windows Xp Pro Sp2...

By default, when I set the system speaker volume using the speaker icon in
the notification area next to the system clock, the ding.wav file is played
through the external system speakers to aid in selecting the proper volume.
For no apparent reason the ding.wav sound was replaced by the standard
system beep sound played through the small case speaker.Additionally, the
Recycle Bin's shredding sound effect has disappeared as well. Under Sounds
and Audio Device Properties, all sounds are visible in the Program Events
Window, and all play their respective sounds when you push the play/preview
icon. The sounds are all there I just can't get at them!

How do you restore the system to normal behaviour. I tried setting up a user
account apart from my own and found that by logging into the user account
all sounds were present and intact - the idea here - to copy or export the
"good" registry values over to my existing account. This did not work.
Simply turning Schemes on or off or saving a Scheme under a different name
does not work either.
(HKEY_CURRENT_USER\AppEvents\Schemes\Apps\.Default\.Default) copied Current
and Default values even though the values present on the existing account
were identical! Is something redirecting sound I am unaware of? The computer
is reportedly free from viruses and adware.

Any assistance in this matter would be greatly appreciated.
Thanking all those who respond, in advance.
FM