When They Say Upgrade, They Mean It: No Clean Installs with Windows Vista Upgrade Discs
In the past, when a user upgrades to a newer version of Windows, users could perform a "clean" install by inserting the upgrade CD and then the old installation CD. The old installation CD served as proof of a legitimate copy of the older Windows OS. The latter is a clean installation of the new Windows OS because users were not copying the upgrade over the older Windows OS. Now, starting with Windows Vista, Microsoft has halted such clean installs with upgrade CD. In order to upgrade Windows, a pre existing Windows OS must already be installed. This poses a problem since it would mean copying the new Windows OS over the older one. The process will work but there will be outdated and useless files left behind by the older Windows OS. This is yet another measure by Microsoft to halt piracy of their software.