Whatever the marketing is, the truth is that Vista is based on the Windows Server 2003 code, which was based on the Windows 2000 Server code, which was based on Windows NT 4 code, which was based on Windows NT 3.51 code, etc.
It's just another update to the NT line, like OS X Leopard is just another update to the OS X line.
well golly gee beav I stand corrected. All hail the Mac - It’s far superior to a reworked windows OS that’s unstable in its first release. Maybe now it’ll get somewhere in the market share ball park Windows has.