I have only used Vista Ultimate 32-bit. I have not had any personal experience with the 64-bit version.  When it was installed, it was a clean install. I don't know exactly how it was installed, as keenart has described, there are various ways of doing it.  I always let my computer tech who builds my systems install my OS and make any windows updates he thinks are necessary. It has always proved way more than worth the very nominal cost.

But I have not had the problems with Vista that others seem to have.