Microsoft Windows 7 SDK .NET 3.5 vs 4

I have seen that there are several different versions of the Microsoft Windows SDK:

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  7/.NET 3.5: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=71DEB800-C591-4F97-A900-BEA146E4FAE1 (1.4 GB)

• 7/.NET 4: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=35AEDA01-421D-4BA5-B44B-543DC8C33A20 (500 MB)

and some others, but these should work for XP and Vista and the server operating systems as well. Now I'm somewhat confused because of the completely different file size of the .iso images. I don't find a complete list of contents on the Microsoft pages and don't want to install both.

Is the .NET 4 version not just a newer version of basically the same thing? Why is it so much smaller, is there something missing or is it just compressed much better?

I'm actually not (much) interested in .NET here, I need samples of unmanaged C++ code for Windows (most urgently the volume shadow copy example). Which SDK would you recommend and why?

The supported platforms are newer, there is no need to ship some OS upgrades.

Documentation is now an optional download via help manager.