My understanding was that the first release of Windows came a long time after the initial announcement, but it was a little before my time.
Microsoft's usual strategy, that no one has explicitly stated yet, is to try and discourage its customers from buying a product by promising the moon 'just around the corner' for a couple years. Microsoft is seen as a better long term bet, and this depresses sales even though it doesn't actually have a product yet, creating a self-fulfilling prophecy of the failure of its competitors.
So when people are angrily referring to Microsoft vaporware, that's what they're talking about.