So far as I can tell, Microsoft has never deleted anything, though they frequently mark documents as “frozen” and no longer maintained, and move them to an archive. To this day, you can still find stuff covering long-retired versions of Office, Windows, and even DOS. You might have to use Google or Bing to help you find it, but it’s all there.
David A. Gray Delivering Solutions for the Ages, One Problem at a Time Interpreting the Fundamental Principle of Tabular Reporting