AFAIK they are all backed up. For the blogpost I used the DX5 SDK docs, DX7 SDK docs, and the MSDN Library from VS2005 (last version to include 9x information).

The VS2008 version purged all API information regarding pre-Windows 2000.

Oh geez, I have them, probably from the 00's. I tried to get into Windows programming, but it was all over my head.

Incredible that a few decades after thinking "All the world's knowledge will be online", we probably have to return to physical libraries to find the knowledge that ended up not being online anymore.