Vista is not a rewrite of XP - its a new bunch of kernel code grafted on top of the XP kernel, which is more or less the same as the 2000 kernel, which is an improved NT 4 kernel, which is more or less 3.5 with some stuff moved from user space into kernel space, giving a whole lot of stability problems due to low-quality driver software. It seems no full rewrite occurred between 3.1 and 7. The only rewrite I heard of was the one between the PDC 2003 video when Microsoft realized they would not be able to finish what they promised (managed code throughout the OS, the eye candy from the Longhorn concept video), threw a=out what they were doing and went back through a less ambitious route.
As far as rewrites go, Win7 seems more or less a rewrite of the Vista cruft that was added on top of the XP kernel.
Vista is not a rewrite of XP - its a new bunch of kernel code grafted on top of the XP kernel, which is more or less the same as the 2000 kernel, which is an improved NT 4 kernel, which is more or less 3.5 with some stuff moved from user space into kernel space, giving a whole lot of stability problems due to low-quality driver software. It seems no full rewrite occurred between 3.1 and 7. The only rewrite I heard of was the one between the PDC 2003 video when Microsoft realized they would not be able to finish what they promised (managed code throughout the OS, the eye candy from the Longhorn concept video), threw a=out what they were doing and went back through a less ambitious route.
As far as rewrites go, Win7 seems more or less a rewrite of the Vista cruft that was added on top of the XP kernel.