There have already been some users that have asked the question "Can Civil 3D 2007 run on Window Vista?" Some have even gone so far as to attempted it.
The answer is, No, NONE of Autodesk's 2007 family of products run on Windows Vista.
As it becomes necessary to replace new computers the issue of operating systems must be addressed. But, everyone should be well aware that Window Vista is currently (January 29, 2007) not an option for Autodesk's production applications.