The tutorial movies require the EnSharpen codec, which you can download here.

Part 9A Fog	QuickTime Movie 2:32	HTML Tutorial	.
Part 9B Sky	QuickTime Movie 2:27	HTML Tutorial	Project at the beginning of this section: VNS 3 DVD: WCS\WCSProjects\Tutorials\YNP\SkyClouds9B.proj
Part 9C Layered Clouds	QuickTime Movie 3:43	HTML Tutorial	Project at the beginning of this section: VNS 3 DVD: WCS\WCSProjects\Tutorials\YNP\SkyClouds9C.proj
Part 9D Volumetric Clouds	QuickTime Movie 1:48	HTML Tutorial	Project at the beginning of this section: VNS 3 DVD: WCS\WCSProjects\Tutorials\YNP\SkyClouds9D.proj