[__david__]

NT4 was the one that took cues from Windows 95—it took the desktop and start button, but it also took the whole grey UI/widget look. NT 3.5 had the same cheesy look and toy program launcher as Windows 3.1. NT4 was the first good windows version (though Windows 95 was the first to be almost as usable as the classic Mac OS).

As far as I remember Win2k was a refinement of NT4, not the same revolutionary leap as 3.5 to 4 was.

[Nikker]

Those are mainly cosmetic changes. The other 99% was a whole new OS.

[__david__]

I'm not disagreeing that Windows 95 and Windows NT are completely different OSes. But I do disagree that it is "just" cosmetic—the desktop and forms APIs are the basis for the UI of the whole system. It's like saying Mac OS X -> iOS was just a cosmetic change, since much of the underlying OS and kernel are still the same.