Adobe CS2 is not Free Software you need a licence to run it legally
System Requirements for Photoshop CS2
by Shea Laverty, Demand Media
While Adobe Photoshop CS2 was released in May 2005, its age may make it an appealing target to businesses -- as of the date of publication, CS2 is still an adequate product for most basic business needs and may be available second-hand for considerably less than the price of purchasing the latest version. Because there are few modern computer systems incapable of running this system, prospective owners should check their system against the minimum requirements before purchase and installation.
Processor
Windows users looking to install Photoshop CS2 will need at least an Intel Xeon, Xeon Dual, Centrino, Pentium III, Pentium 4 or comparable CPU in order to run the program. Mac users will need at least a G3, G4 or G5 PowerPC processor.