I've never known so much confusion over a product line....what were Nvidia thinking?!!!
An Nvidia driver ...this ought to be simple enough, except there's a huge number of versions about some compatible with the HD, some not.
An Nvideo DVD decoder Codec that doesn't necessarily work with just DVDs (but also for example harddisk media files). Also the different version 9gold platinum), from what I can gather just give you different audio decoding capability? They're related page talks about H.264 (HD), butthen makes no mention of what you actually needto get rocking....
http://www.nvidia.com/page/purevideo.html
An NvidiaPure HD....***? still don't know what that means!