I would say Windows 3.1 -> Windows NT + Windows 95/98 -> Windows 2000. The transformation from the sausage factory of the indestructible, but inflexible, NT an

I would say Windows 3.1 -> Windows NT + Windows 95/98 -> Windows 2000. The transformation from the sausage factory of the indestructible, but inflexible, NT and the fragile set of hacks which was 95 into 2000 environment was the real story in all this. This combined with to migrating from Netbios and NT Domains to tcp/ip and active directory was really the basis for everything they've done in the 21st century. They did more in those 6 years than they've done in the 20 years since.