PowerPC :: Reinstall OSX On G5imac Error Message Can't Be Installed?

So, husband booted from OSX disc, wiped computer using disc utility, now it won't reinstall from the same disc. He says the error message is "Can't be installed on this computer." When I asked what disc he used, he says it was "the only one that let me start up from it." I believe it is disc one of the mac osX install disc version 1.0. He said the disc that was labeled for the G5 wouldn't let him boot up. He is ranting now about there being no difference between PC's and Apple. If you can, please tell me how to fix this, or at least how to get the disc out while it is the computer's startup disc. He's about ready to to hit the wall.

Update: Got the disc out and am now attempting to install from G5 OSX disc but getting the "this software cannot be installed on this computer" message. Why? It is the right disc!