Run Adobe Photoshop CS3 on 10.4.7
The CS3 Installer does not let you run Photoshop on any other system but 10.4.8. If you have two machines, and one has 10.4.8, just simply copy over the /Application/Adobe Photoshop CS3/ folder and /Library/Application Support/Adobe folders... and magically, it will work.
If it says something about Invalid Product key or Invalid Install - see this link, how to manage this problem :)