How do I upgrade to Windows Vista?
Upgrading to a 32-bit edition of Windows Vista
You MUST have an activated, genuine edition of Windows XP or Windows 2000 installed on your computer to use the upgrade disk.
You cannot start the upgrade process by booting the DVD.
Start your computer and boot into either Windows XP or Windows 2000. Open the installation DVD from My Computer if it does not start automatically, then follow the instructions on the screen.
You must perform an upgrade install - the custom (clean) install option is not available.
Upgrading to a 64-bit edition of Windows Vista
You must have an activated, genuine edition of Windows XP or Windows 2000 installed on your computer to use the upgrade disk.
Insert the installation DVD into your DVD drive and restart your computer. Press a key when prompted to begin the installation process, and then follow the instructions on the screen.
You will only be able to perform a clean install of a 64-bit version of Windows Vista, even if you have Windows XP x64 edition installed on your computer.