I have CS-3 on a disc, was using Mac Leopard. Just bought a new Mac Mini with Mountain Lion and when trying to install from the disc, it did not install but put a message "contact Adobe". The "chat" agent says he only deals with CS-6 and CC, suggested I try asking here.
Download a trial version from http://prodesigntools.com/download-adobe-cs4-and-cs3-free-trials-here. html
Follow the Very Important Instructions (steps 0 to 6) on that page first BEFORE you click the download links.
Install the trial then enter your serial number to license it.