Hello , I know that you cannot install an OS on an iMac earlier than the one it came preloaded with. Does anyone know if it is possible to get round this by installing the earlier OS on an external HD and then use that to boot up? To be more specific would it be possible to install Mac OS 10.2 on an external HD and then use that to boot into a powerPC G5 that came pre-loaded with Tiger. I know it's a strange request but I've just got a thing for the pinstripes. Thanks for your help.