So if you purchase Home Premium, select Home Premium. This will install Vista as a 30-day trial. Instead click on the Next button and continue with the setup.
When you get to the setup screen, start a new setup of Vista. Boot your computer form the Windows Vista Upgrade DVD.Paul Thurott has discovered from internal Microsoft documents another method that you can use to perform a full install. Another issue that occurs is that you will invalidate the XP product key that you are upgrading from. What this means is that there is no true way of doing a clean install from a formatted hard drive as when you enter the Vista product key it will tell you the setup must be run from within the previous operating system. No longer can you boot off of the setup DVD and just insert the media of older versions that you are upgrading from.
As many of you are now finding out, in order to upgrade your copy of XP to Vista, you need to have XP currently installed on the computer and the setup program must be run from withing XP.
