"How you acquire Windows Vista play a large part in any decision about how you will actually install the operating system. At a high level, you have the following basic choices:
Clean install. With this method, you boot the PC from the Windows Vista install DVD, run interactive Setup, format the PC's hard drive, and install Windows Vista as the only OS. This is probably the rarest way to get Vista on a PC. You can use a "Full" or "Upgrade" retail version of Windows Vista to perform a clean install, though you will need "qualifying media"--typically a Windows XP or 2000 CD that proves you qualify for the Upgrade version."