After erasing my No 1 drive to get rid of Snow Leopard (by using the erase function in Disc utilities after booting up with the Snow leopard disc), I tried to reload Leopard, but no go, the message says 'Mac OS X cannot be installed on this computer'! What have I done wrong? have I done anything wrong? apart from my determination to get rid of SL. I have twice lost the complete contents of iPhoto, that, coupled with Safari and iPhoto crashes, my preferred font display changing willy nilly and other suspicious behaviour has pushed me back to the stable platform that I used to know 'Leopard'. Any help guys, it appears that unless I use a drive with SL on it I lose my computer.