I was impressed by this response at the time - Adobe were clearly looking after their customers. They set up a support page where you could enter your original serial number, and receive an activation-free version of the installer with a new serial number in return. I seem to be one of the lucky few who stumbled across the activation-free version of CS3 that Adobe briefly made available to licence holders after the activation servers were taken down. It is indeed perfectly functional (with a little tweaking of compatibility settings), a fast, powerful editor that works as well as it ever did. I installed CS3 on a Windows 10 system yesterday.
