Activating Photoshop upgrades on new computer

[NigelC]

This is probably a stupid question, but if you deactivate PS on an old computer and activate on new one, since new one does not have previous PS versions, how does upgrade determine it is a valid installation, or does that just happen once when you first install upgrade?

[francois]

This is probably a stupid question, but if you deactivate PS on an old computer and activate on new one, since new one does not have previous PS versions, how does upgrade determine it is a valid installation, or does that just happen once when you first install upgrade?

Nigel,
If I remember correctly, when you install the new software, the installer will ask for the previous version serial number.