Windows 7 DirectX10 & DirectX9

I have been seeing a disturbing ammount of talk on the web, and it could have been there and I ju st didn't notice, about *d3d9* files issues. People talk like DX10 & DX11 are just upgrades to the DX lineup. That is not the case at all. Just because Vista comes with DX10 and 7 with DX11 doesn't mean that they come with all the files needed to run game made for DX9. I have seen many times when people would talk about uninstalling DX*, and installing DX9. That is just not possable at all. The version that the OS comes with is what you have to use. Though there is hope, all that needs to be done, in most cases, is to run the DX9 install that comes with the software and that will add the needed files in the right places. Now this is not to say that you can go to the DX website and download a copy, that may not have all the needed files. That is why I say to use the install that comes with the software. What I am trying to get at is, has any one else seen this or is it just me? Also why is it that not more people are using this advice? I know a little about computers but I am far from a Microsoft MVP. So why are they not telling people to do this more offten. The tools are there and that could be the simple fix that takes care of the problem. Has anyone else seen this and what are your thoughts on it?