[psd1]

Longhorn was a significant rewrite, actually. The two big upheavals in windows history were: 2000, which essentially scrapped the 95 lineage in favour of NT; and Vista, which kicked a lot of 3rd-party crap out of the kernel and added a quality gate for drivers.

[umanwizard]

The Win95 lineage still existed, in the form of Windows ME, alongside 2000. XP is when they got rid of it and unified the two product lines.