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#1
Generally, the downgrade goes OK but "murphy's law" always is present.
First step is to "refresh" the sound. Go to the Device Manager, RIGHT click on the entry for your sound driver and then LEFT click "Uninstall". DO NOT uninstall the drivers. Restart the PC and when Windows starts it will detect and reinstall the sound. Any Windows sound corruptions will be fixed.
If that doesn't fix it, reinstall the sound driver (from Gateway).