... Of note: Windows 2000 cannot be upgraded to Vista.
While Windows 2000 Professional customers may purchase a cheaper "upgrade" copy of Microsoft next-generation operating system, Windows Vista must be "clean installed," which means users will need to back up their files and data manually and then copy everything into place. Applications will also need to be re-installed. ...
Going to correct myself since it would seem i was in coffein overdose at the time of writing. You can USE the vista update edition, but you will have to install the OS using a clean install, rather than udating the already installed w2k.