First Quit photoshop cs3
In Finder press Go on the menu bar>Applications and in the Adobe Photoshop CS3 folder click on the
Adobe Photoshop CS3.app and either press More Info or Cmd+i.
Then in the Get Info dialog uncheck Open using Rosetta
I notice your other posts say photoshop cs3 won't open after upgrading from 10.4 to 10.6
Do you get any error or crash messages when trying to start photoshop cs3?