Leopard users get snow leopard for 30 buck and tiger users have to pay the usual 129. So how would they know if you have leopard or not? I have leopard on all my macs, but the only install disk I have is the one that came with my new macbook. The others came with tiger (all intel) and I um, used a friends leopard disk on those. So will I be able to upgrade those for $29?