Vista - intel d945pvs onboard audio works before reboot?

I have a vexing problem. My audio works great just after an automatic update,
before I reboot the computer. The sound is perfect thru the analog plugs and
the digital optical toslink as well. As soon as I reboot the audio goes to
slow mo. It sounds like a tape running to slow.
The Question is how do I stop the vist hd audio driver from loading to see
if that is the problem? If I disable it it reports no audio device installed
thus there is no sound.
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Vista x64 HD audio, Intel 645pvs,pent4 3ghz, spidf optical