Adobe shut down the CS3 activation servers in 2018. You cannot simply enter a serial number anymore. However, Adobe released an official "CS3 Discontinuation" workaround: .
(released in 2007) was a massive leap, introducing 3D toolsets and "Smart Filters" for the first time. "-REQUESTED-" Adobe Photoshop CS3 Extended -REQUESTED- -blaze69-
"Not enough RAM" error on a 32 GB machine. Fix: CS3 is a 32-bit application. It cannot use more than 2 GB (3 GB with the /3GB boot switch in XP). Do not expect to edit 4K video layers. Adobe shut down the CS3 activation servers in 2018