VIA Envy24PT sound card driver loads at startup properly 9 of 10 times

Windows XP Home Edition SP3 With all the latest MS updates and hardware
driver updates including the latest and correct driver for the sound card.

Onboard sound chip is disabled in BIOS and the driver for it is not
installed.

The sound card, Chaintech, Envy24 Family Audio Controller WDM, is
installed/seated properly and uses the (virtual) IRQ 16 exclusively. (It
shares an I/0 port with the standard PCI-to-PCI bridge)

Every now and then when my computer boots into Windows and the sound driver
loads I hear the normal "pop" of the speakers then a jarring squeal or tone,
sometimes very high-pitched, sometimes its medium pitched, but I have to
shutdown and restart the computer. Or, I can uninstall the driver in device
manager and reinstall it if Windows doesn't do it automatically, and that
stops the squealing noise as well. This has continued to occur since I
puchased the card over a year ago, and, after two reinstallations of this
Windows OS.

All the drivers that load for this device are signed for MS Windows
Hardware Compatibility and no conflicts are shown in device manager, system
information, or in DirectX diagnostic tool.

Any ideas about what might be causing this or heard of similiar experiences?