SndVol.exe

How to restore Volume icon in the taskbar?
The volume icon from my Windows XP taskbar has suddently vanished. When I open "Sound and Audio Devices Properties" from the Control Panel, and check the "Place volume icon in the taskbar" checkbox, it displays a message saying "The volume control sndvol.exe /r is not available. Please install it using the Add or Remove Program in the Control Panel".
I did not find any option in the Add or Remove Program to install the volume control. I also did a search on entire hard disk to locate the file sndvol.exe, but could not find it.
Could someone tell me:
(1) how to go about re-installing this program and the icon, and
(2) what could be the reason for its sudden disappearance?

MVH/sabir