You just purchase the upgrade, and the installer will either locate your existing Photoshop install or ask for your Photoshop serial number (if it isn't installed) - at least, so it was for the 1.0 version of the Creative Suite (i.e., with the 7.0 version of Photoshop, etc.), which was actually launched in Italy (maybe to try to persuade people not to "pirate" the Adobe flagship products?) about a year ago. The upgrade procedures for the new (PS 8, etc.), "international" version of Creative Suite should be identical, as it still uses the same VISE installer...