Which operating systems can be upgraded to Windows Vista?
You can upgrade from your current edition of Microsoft Windows XP or Windows 2000 to a corresponding or better edition of Windows Vista by purchasing and installing an upgrade copy of Windows Vista. Depending on which edition of Windows you are running and the edition of Windows Vista you would like to install, you have two options for the installation process:
You can upgrade in-place, which means you can install Windows Vista and retain your applications, files, and settings as they were in your previous edition of Windows.
Upgrading to Windows Vista with a clean install means that you should use Windows Easy Transfer to automatically copy all your files and settings to an extra hard drive or other storage device, and then install Windows Vista. After the installation is complete, Windows Easy Transfer will reload your files and settings on your upgraded PC. You will then need to reinstall your applications.
The table below outlines the upgrade options mapped to the different Windows Vista editions.
If you are currently using Windows 2000 Professional or Windows XP Professional x64, you are eligible for an upgrade copy to a corresponding or better edition of Windows Vista, but a clean install is required.
For versions of Windows earlier than Windows 2000, upgrade copies are not available. These earlier versions of Windows require you to install a full copy of Windows Vista.
If the edition of Windows Vista that you choose to install will result in a loss of functionality over your current edition of Windows, a clean install must be done or the installation must be completed to a new partition on your computer.
Note: This information provided by Microsoft.